Hi,
I'm setting up a magical effect that will change the size of the user. More specifically, it will shrink the user to the size of a mouse. Looking at the MuCo guidelines, changing size has a Base of 3. But does this take into account how big a change the effect will have? Should I use the same Base level for a change in one size and a change in 10 sizes?
E.
i use this:
+1 grow or -2 decrease in size = 3 base.
For each +1 or -2 => +1 magnitude
So to become +10 in size is a 40 base.
or become -5 is a base 5
It's not a Hermetic guideline, but a level 10 Conjure effect (Realms of Power: Faerie) can reduce a character's Size by 10 levels (or rather transform the character into a Glamour of that size)...
Anyway, I'd definately consider allowing a Hermetic Magus to use the Conjure guideline with a Muto Corpus spell. Perhaps imposing a 1-2 magnitude increase for the unusual nature of the effect...
For reducing, my guidelines is for a -10 size a level 20. So it's not too far from level 10 (conjure) +2 magnitudes 
.
I consider growing more difficult than shrinking (because, a big character is less wounded for the same damage and that his strength grow by +2 there where his quickness decrease by -1...)
I've been wondering about this too. The Preternatural Growth and Shrinking spell gives what looks like an arbitrary +1 "because the spell allows growth of two types of shrinking." So if your spell is intended to shrink the target by a very large degree, but to only one size, is no magnitude increase warranted? A knotty problem.
It came up because we recently faced an antagonist who was magically cultivating bee products (I'm not sure if this was a published scenario or not, so some of you might be familiar with it). My sodalis and I became completely fascinated by all the bee-related stuff and determined to A) establish bee colonies in our covenant, and B) devise a means of shrinking ourselves to bee size so as to allow us to observe the process by which the bees choose their king bee. Eventually, I hope to execute C) awaken human-level intelligence in a particular bee colony, to observe the distinctions between the base nature of bees and that of humans that allow bees to cooperate so efficiently.
Hi,
I'd allow reducing to any fixed size. (And for increases, I'd just account for the usual rules on size. So increasing a person to Size +3 costs an extra magnitude, as for any large Ind.)
Anyway,
Ken
The most convenient way of changing size is changing substance as well (see MoH, p. 12). Changing a pool of water into a tooth is level twenty.
Hi,
slow grin Yeah. Of course, the Target needs to encompass the pool, and if the pool were turned into a +7 giant, the Ind would need to be encompass the +2 magnitudes needed for Corpus....
Anyway,
Ken