Kind of similar opinion, but I want us to have an agreed decision on how we're hadnling it for the Grimoire.
I also think we should note at the beginning of the final that this was fan-submitted and fan-reviewed, so everything should be taken with the understanding that we tried to be as true to the Core RAW as we could, but each Saga should use their own interpretations as to what they accept.
I have to say that coming into this project, I didn't realize how enlightening it would be.
Sure, myself, am not doing much of the critique, but seeing the discussions both here, and in the comments on the document, I love it, and I feel like they are very eye opening.
And I want to thank everyone who is participating with the critiques.
A wall is not just a big rectangle. Someone has to figure out things like height vs thickness, foundation, slight degree of angle, etc. Ice forming down the side of a wall is not forming a wall, it is forming a sheet. Taken and plopped somewhere freestanding it structurally would not make a very effective wall. Far to thin in cross section to the point it might collapse under its own weight and poor if any foundation.
I look at it as even for simple shapes, would it take some crafting or architectural skill to make it effective or could would something you could find work.
The actual closest thing to a wall ice forms naturally is an 'ice berm'. I would have no problem with a spell using one of those as a "wall" but even with saving the magnitude for slightly unnatural shape you would have to spend at least one more on size and it would still mostly not be as effective as a wall.
EDIT: Just wanted to add that I am on the last two pages of ReAq but hitting a little burn out after the roughly full work week I put into getting through Aquam. Will try to finish it up then take a few days off before starting work on Auram. Will still be around and posting comments/discussing.
If I can keep up even half the pace I will make it through the last 8 Forms in... three months. This project is big and we are all crazy. The good kind of crazy but still... you know... crazy.
I agree with your assessments on ice forms. Though I did take a look at Creo Terram for a niggling idea.
Creating earth in an elaborate shape or with some unnatural property is one level of magnitude higher than the listed guidelines.
Creating stone doesn't care if the shape would form naturally, it cares how complicated or elaborate the shape is. Why does a wall-shape of ice need the bonus magnitudes to be in a wall, when stone does not?
Different Arts have different guidelines and are often a different Base for doing to same thing. Terram only needs the additional Mag for elaborate while Aquam needs it (higher Base for water, +1 Slightly Unnatural for ice) for anything not natural when you are looking at Creo. The same two Arts looking at Intellego, the Base needed to see an object/water and its surroundings is Base 4 for Terram and Base 3 for Aquam. Aquam also has a Base 2 for just seeing water.
Depending on what Form you are working with some things will be easier and some harder. The game was designed this way and has been going back to at least the 2nd edition.
Have you considered a Wiki? It would permit discussion pages on each individual spell and come together more quickly, and stay current.
I figured out what some of my issue was.
I really didn't like +1 for unnatural shape - and it shouldn't be there, I think. Instead, looking at the CrAq guidelines, it should instead just be base 4, create water in an unnatural shape, rather than base 3 +1 magnitude.
For everyone who hates doing the math for calculating sizes and shapes, I would strongly recommend using Omnicalculator. Specifically their 3D geometry section.
You can use it for easily calculating out nearly any shape, start with the total volume, and get what a dimension would be in another unit of measure just by changing the unit to use from the drop down menu for that dimension.
Something that needs to be discused, derived spell Bases. It has come up in the thread that creating ice in an unnatural shape should be Base 4. That is derived from the existing Base 3 "create ice in a natural shape" and adding "+1 Slightly Unnatural shape" to it. It cuts down on the text, since it is easier to list just Base 4, and helps avoid confusion on spells that might have multiple unnatural modifiers.
So we need to decide if we are OK using derived Bases like this and how we will mark them in the final document. My vote is "yes we can as long as they are achievable by RAW" and to create a small section at the beginning of the document that describes the derived bases we used along with the math for how we calculated them.
CrAq Base 4 "Create Ice in an unnatural shape" is easy, as raccoon pointed out. It is not in RAW but can be easily calculated from RAW.
EDIT: Maybe include a * at the end when we use it in the document. So the above would be written "Base 4*"
EDIT to EDIT (avoiding a new post): There are several Aquam spells in the MuAq section which transform one liquid into another that uses a different Base Individual. Per published spells doing this causes a shrinking or expanding based on the ratio. If you changed 10 cubic pace of dirt to stone there would only be 1 cubic pace of stone. Transformed 100 gallons of water could become 10 gallons of fruit juice or 1 gallon of wine. Many of the ReAq spells attempt to get around this shrinking by using a higher Base "into slightly unnatural liquid".
I believe this is workable since that is the same Magnitudes as adding a +1 Size to expand the liquid if it only crosses one step on the Volume Conversion Guide. While I have been noting that in my comments on them I realized that for things that cross two steps (water to wine) it would require +2 Size worth of expansion to keep the total volume the same. That would mean it needs to use the "change into a very unnatural liquid" to keep it inline.
So we need to choose ether use the "natural to natural with +# Size growth" or "natural to slightly/very unnatural" to keep things consistent. I am fine with ether option though I believe how RAW is written it should use the higher Base. "Water to shocking pick liquid that cause hallucination" could just as easily be "Water to amber liquid that causes drunkenness".
Actually, I was fighting against saying '+1 unnatural shape' as a magnitude at all. Don't like it. If it exists for ice, it should be enforced for other forms as well. The reason why is because there's no evidence of +1 for unnatural shapes, only +magnitude for intricate/elaborate shapes. My logic is tied to extrapolating bases that actually exist in RAW.
and
There is evidence for creating slightly unnatural liquids and very unnatural liquids with +1 and +2 magnitudes, but those don't actually talk about the shape, only the properties of the liquid [and I think, like Terram earth, it should be included in the base]. I don't like having a '+1 magnitude for unnatural shape' because it opens up putting that same penalty-magnitude into other arts.
It feels kind of pedantic, but I also very much feel we should do things as properly as possible in form, not just in final numbers.
The Guideline is in HoH:S, page 34.
Creo Aquam Guidelines
Level 3: Create ice in a natural shape, such as a floe or icicle.
There is nothing else provided. The modifier of "+1 Slightly Unnatural shape" is based off of all other guidelines that use an unnatural shape being a single magnitude more than a natural shape. If the group wishes to use +1 Complexity instead then I have no issues with it. It needs to be decided on and expect to run into comments stating the contrary for a while since there are already entries bringing it up.
You should check the guidelines then:
Creo Herbam has:
Base 3: Create a wood in an unatural shape (a living wall of wood)
Creo Ignem has:
Base 5: Create a fire doing +5 damage in an unnatural shape (ring, sheet) or covering an object.
Base 10: Create a fire doing +10 damage in an unnatural shape (ring, sheet) or covering an object.
Base 20: Create a fire doing +20 damage in an unnatural shape (ring, sheet) or covering an object.
This support my opinion.
The next question would be if the unnatural shape has to take context in opinion. To use the first example from our CrAq section is a good example: It creates an icicle, free-floating, at touch range. Is this natural? It totally is a shape that could be formed, naturally without human intervention... except that it would have to be hanging from a thing, rather than just in someone's hand. Or sticking out at a 45 degree angle from the ground, or on a wall.
Dagger of Ice (HoH: S pg 35) uses the Base 3 "Create ice in a natural shape, such as a floe or icicle" guideline to create an icicle in mid air and fling it at a target. The spell you're discussing* sounds similar, so is probably reasonable in that regard?
I don't think I've got access to the spell list to see it, but I'm assuming it's not Dagger of Ice itself you're talking about even though it's the first item in the HoH:S CrAq section as that's Voice range and canonical.
@raccoonmask
Just saying sorry ahead of time for blowing up your two CrAu spells. The Overwhelming Gloom And Damp only needs Size to be as large as described, while Calling the Spite of Vulcan has the potential of allowing 100 pace diameter +10 damage CrAu(Ig) fireballs with no Size if allowed without changes.
I look forward to checking it when I get Auram. Trying to finish up Aquam.
Here to annoyingly quibble about rules again!
Since we have a lot of 'transform water into x' spells in MuAq, I figured I should bring this up here.
While I mostly agree with Troy's statements that transforming Water to Wine causes the liquid to shrink in size, I found myself looking at Earth that Breaks No More (MuTe 20), which turns earth to stone with no mentioned size change [and I checked errata, changes the ] - we should assume the spell has some weird nonstandard effect, or am I missing somethihng?
I also had a weird mental image of transforming Wine to Water, which obviously causes nearby barrels to explode into a hundred times their volume, drowning people involved.
While I’m not active with vetting spells for this project a solution for the shrinkage due to base individuals I’ve seen proposed was either limit the amount the spell can change to the smaller volume or add one or more size mags to account for the change in volume the spell can handle on the smaller base individual end of things. I don’t actually think the volume of the liquid should change but the spell should fail if it will be too much volume to be a valid target during the spell’s ongoing effect. Beer is not “denser water” and the general effect for most forms of going outside the limits of a valid target due to insufficient spell size is just that the spell doesn’t work. If I want to change some water into a highly corrosive or poisonous liquid all I should need is that thimbleful of liquid I would have at the end, I’d rather not need a whole lake or pond to get that thimbleful and if you do need that whole pond then why does Aquam work so differently than all the other forms when it come to physical muto changes?
IIRC it was @callen who proposed something along these lines and if it was maybe he could explain it better.
EDIT: On another note, thank you all for doing this work. I greatly appreciate it.
I don't really have anything to add, but am super grateful this project is continuing. 
I think, annoyingly for me, Muto Terram has an example of turning a cubic pace of stone into a small gemstone in the guideline sidebar, but then has Earth that Breaks No More.
@raccoonmask : My understanding is that Muto can make different types of change. One is when you change the Substance other is when you change Quality. (A&A p. 22.)
When you change Substance you can make dirt as hard as stone without actually changing it into stone. It is dirt, but with great hardness.
When you change Quality you can change dirt into stone, or water into gem. In this case you will experience quasi-real change and the matter will change in its amount.
That's why the Core Rulebook says separately in the MuTe GL at Level 3 the following things:
Change dirt so that it is slightly unnatural (requisites may be required).
Change dirt into a liquid or gas (with requisites).
Change dirt to stone, or vice versa.