I would allow it, so long as it was cast in the first day. If the ring duration has already gone beyond a day then the MuVi would just end the now over-extended spell.
Well that certainly removes the concern about the ring spell having lasted longer than a day...
Ok this is going to sidetrack the core discussion but what makes you say that? I find that many creo spells are well fitted for it. I would go as far as to say that all healing rituals should be circle as a target.
W
Insert about Targets and Creo on page 113. Valid Creo spells that create things are T:Ind or T:Group.
I know a spells in Hermetic Projects, Conjuration of the Mystic Cog, uses the T: Structure, but even correcting the spell for T:Ind (Or Group) with size increments, the level is still the same.
Ah! Paradigm is shifting! Thanks for the enlightment but it is somewhat strange that Only creo has this limitation...
So just to be canon, lets use as an example:
Touch|Ring|Circle light spell (MuTe(Ig)) and wanted to use a MuVi spell to change the duration from Ring to Sun. Is this enough to bring it to General +1 or can this fit into the "superficially" bucket?
Can chnaging only one parameter of the spell without changing the level of the effect, target or description of the spell, be considered a superficial change that is no greater than supressing the sigil or changing the description (Turning to a dog instead of a pig for example) ?
W
Just a minor point - the "+1 magnitude" is likely spent on making sure the MuVi spell is touch-ranged. I think the theory is that the spell is 99% finished, and basically hanging in the air in front of the magi, and that the magi actually does have to reach out and touch it in order to modify its effects. One that is offensive (ie, reaches out and affects an enemy's spell) would have to be voice or Sight-ranged.
But yes - what you are talking about is what we're discussing.: I'm arguing from a fairly strict rules definition that because the parameters don't change, then by DEFINITION it's a 'superficial' change.
Others are arguing that the end result seems to be something non-superficial, and that therefore it should be considered a moderate change. To which I would respond "changing a spell from duck to pig doesn't sound superficial to me, either." So ultimately for me its an issue of consistency.
My main evidence is that we all seem to agree that "This may not change the primary effect of the spell" implies that you can change the implementation of the guideline, but not the guideline itself. OK, fine. Changing the guideline is spelled out in the Moderate and Complete versions. No problem.
To be consistent with that, the second part of the phrase (This may not change the primary effect of the spell, or its power") should also imply that you can change the implementation of the power level, but not the level itself. Because similarly, changing the power level from +1 and +2 is spelled out in the Moderate and Complete versions.
So - it seems a fairly consistent interpretation to me:
If you keep the change completely within the guideline or the power level, it's a superficial change.
If you change the guideline to something similar (within the TeFo) or the power level to something similar (+/- 1), it's a moderate change.
If you completely change the guideline (outside the TeFo), or completely change the power level (+/- 2), it's a total change.
It's not even all of Creo, only a subset.
I can really recommend reading that box a few times 
Absolutely!
..but that's kinda my point.
Changing a parameter from eg. T: Individual to T: Circle is (to use the same notation) by DEFNINITION a change of parameters.
It doesn't change the level (of effect nor parameter) but it certainly changes the parameter.
To me, this doesn't seem superficial.
Also, as has been pointed out above, superficial change is never defined, so nothing is by definition a 'superficial' change. We can set up examples of what would be superficial changes and indeed have above (casting sigil, exact details about a transformation), but we cannot simply apply a definition. If we could, this discussion would've been over a long time ago.
Indeed.
Ah - bit of a misquote on my part. The actual text for a superficial change is "This may not change the primary effect of the spell, or its power". So parameters aren't actually discussed. So as long as the power level doesn't change, my argument is that you can change the parameters. If it DID say "may not change its parameters", then yes. I would agree with you, if only from a computer programming perspective.
But rather than never being defined, I'd say that "superficial" is being defined in the negative - we're given 2 limits: "does nothing" (implied on the low side), and "may not change primary effect or power" (on the high side). On those axes, in between, it can do whatever the spell designer likes, as with any other guideline.