Good maneuverability, DR 5/magic, SR 10? or 10+HD? Other than that, just change their lairs from "peaceful placed" to "peaceful places," and I think we're good to go.
Yes, sounds good. I'd say that they're otherwise almost identical copies. Even the advancement will be the same if we take out the bit about changing into a greater plumazotl at 6HD. What do you think? Should we add any other abilities? This is kind of boring if we don't, I guess.
I'm not sure if we need to add any additional abilities, since they already have the better spellcasting power. If you have an intersting idea, though, pass it along.
AC needs to remain at 17. With the lower Dex and loss of size bonus, we need to make up 4 points of AC. Wanna go with natural armor, or maybe a deflection bonus?
Increase Damage reduction to 10/magic?
Skills: Concentration +9, Listen +15, Spot +15, 1 more at 9 ranks