okay, this one came up last night...
A player wants to create a normal creature, but wants to modify the stats for said creature (quickness, 'int', stamina etc).
We all went over it, and really couldn't come to a conclusion..
What does everyone think?
Can it be done with one spell?
Does this take two spells? (more)
Personally I would say that increasing a characteristic by 1 point would add 1 magnitude to the CrAn ritual. If he has a sufficient CrAn casting total he could maybe get two or three different stats raised by one, but it will get costly.
Another route (borrowed from my suggestion in the horses thread) would be for your player to get a few of his sodales together and have them all cast Wizard's Comm together and (provided the total of the WC ritual is twice the full score of the CrAn ritual, with whatever added mags are required for adjusted stats) thus get to divide the casting target number for the CrAn spell by the number of magi in the Wizard's Comm.
Since heightened characteristics for animals is still a CrAn effect id say just do it in one shot.
Edited to add: Having just looked at the actual CrAn guidelines my original estimation of 1 point for 1 mag might be deemed by some Sgs to be generous since CrAn characteristic boost effects start at 6th magnitude and thus should be +2 mags for 1 point, but since the creature isnt magical it should be left to SG discretion how much he/she will allow depending on how high a player wishes to raise such stats.
For multiple 1 point stat raises it will already get pricey fast at +1 mag.
a though thats not totally fleshed out yet....
would combining some sort of finesse role or amount you exceed the casting total, the section on mundane beast in the bjorner section, and the difficulty levels in city and guild for making exceptional items make sense?
I dont have city and guild to look up the details on difficulties...assign a difficulty to an average beast, say 9, a superior item/beast as 12, an exceptional beast 15. for each 3 points you exceed the difficulty you can add a virtue as mentioned in the bjorner section which would allow increased stats...
Yup, that's a good one, you must even be able to combine some heartbeast refinement rules with creo magic to determine the abilities of your creature
Well I suppose there's more than one way to skin a heartbeast! 
Somehow though I think that while the alternative suggestions are certainly creative, they are tad fast and loose with the canon methodology of CrAn beast creation. Whatever your SG will allow, though, is the route you should take. 
Except that when creating natural objects, the item is already a "perfect" manifestation of that form. (That's from somewhere in the Creo guidelines, I'm sure.) What "perfect" means, however, is unclear.
Hence the problem...
Does perfect beast have +(?) quickness...???
This is mentioned on page 77 under the descriptions of Techniques. To be precise the paragraph refers to natural things (trees, animals, fire, etc) as opposed to artificial (man made things) such as "bread, swords, etc". In the former instance, the thing made is a simple form and thus a perfect example of its kind (without any finesse roll involved). The latter instance involves finesse because it is a complex form (i.e. composed of several combined forms).
This is where semantics gets a bit hairy. The animal in its common form with its normal characteristics according to its type, would be deemed a "perfect" example. Nevertheless, Creo magic may improve upon this perfection by enhancing one or more characterisitcs. Thus you get a Perfect+ example of a form.
And subsequently logic and the meaning of terms flies right out the window ! lol.
With the higher magnitudes in 5th ed of giving Attribute bonus, it should add more than a single magnitude to the CrAn spell.
Of course, this depende on what the creature already has. IIRC the magnitude is 6th (or 7th) to give +1 to a max of +1. So if the creature already has +3 Quickness, it's a 10th mag spell to add another +1.
As I see it, you shold look at what level spell you had to cast, had the animal been natural or already been summoned, and then boosted afterwards.
Yep, this is precisely why I added the comment to my first post. It seems to me that the best and likely only way to create mundane anmals with improved characteristics (whether in one spell or several) would be to do it as a group ritual process using Wizard's Comm and thus bringing the target casting total down to a manageable level.
Just remember to note that if you choose to use more than one spell (one to create the normal type of beast and addition spells to raise each characteristic by +1 until you reach the levels you want for each characteristic), then be sure to keep track of the warping points you will be putting on the creature.
Well, the real problem there, is the fact you use a LOT more Vis...
One spell uses Vis, once...
Very true, but one spell can also be of such high magnitude it is beyond the capability of one magus to cast.
How would you work an animal of exceptional breeding vs an average animal? Say a show dog vs a mut, or a racing horse vs a nag? The "improved" version is still very possibly by mundane means.
I see the principle of what you are asking but suggest that your comparatives are not equatable even in mundane terms. A "show dog" is a pure blooded offspring from one particular breed of dog, a mut is a random uncontrolled assortment of breeds mixed together, so too I would strongly believe, with race horses versus plough horses.
In terms of the "perfection of forms" one must limit the focus of the examination to all examples of that particular breed (i.e. the perfect characteristics of "race horses"/"show dogs", etc and enhance further from that basis.
If you are planning to create a given animal type , I would personally demand as SG to know which species/subspecies you are intending and then determine base characterisitics for that breed (provided it even existed or was known in the Ars age) as its "average" base.
Your original question, nevertheless, does not concern what may be achievable with mundane breeding methods (which in any case often take several successive generations of breeding (or even cross breeding) by animal specialists to achieve significant characteristic enhancements), but rather what you could do to MAGICALLY create an animal with significantly superior stats.