Gez said:
In general, when your racial ability adjustment is negative, the result for 18 is equal to the double (average 8 gives 16, average 6 gives 12, etc.).
Really? I am unfamiliar with this rule. Is it a Savage Species rule?
I though you just took the score and subtracted 10 to get the racial modifiers for a monster as a PC.
As for the CHA modifer, I wouldn't have a problem with making it "0" based on a PC race for a mouse - they have -4 net physical stats anyway, so +2 mental stats leaves them still with a net negative total, especially when considering that physical stats are valued more highly by WotC designers. Balance-wise it's fine, and logically it's okay, too. I see no reason why the aveage charisma for a PC Race "mouse" should be only 2-4.
You might note that they should have a climb speed of 15 - as noted in both my examples of how to construct a PC mouse.
A few other general comments on this pretty cool concept:
I don't know about them as sorcerors, but they'd make mighty fine monkish scouts. They've got a nice hide bonus as well as a nice racial dex and wisdom bonus - a starting Dex of 22 and/or Wisdom 20 is possible!!.
I'm thinking monk because if you go without any equipment you are very, very hard to notice as being any kind of threat (oh look, it's just a mouse) but would be hard to kill with a possible
starting AC of 29: 10 +8 (size) +6 (Dex) +5 (Wis). You'd only have Str 6, Con 8, Int 8 and Cha 8 (if we go with a "0" modifier) in this case, so hit points and Fort saves wouldn't be very good, but AC, Reflex and Will saves would be great! AC would even be 29 vs. touch attacks and 23 flat-footed.
The biggest single problem will be grappling - the size modifer of -16 will be a killer. Best to take the maximum possible ranks in "Escape Artist" to offset this problem - it's a Dex-based skill, so that will help.
I see sorceror as being only moderately successful. This class would not play into the strengths of being a mouse at all - it might not be very survivable. Too slow to get away, too weak and small to have much of a chance against anyone simply grabbing and crushing you (grappling - a likely -18 to the grapple check, -16 size and -2 Str).