Diirk said:Alter self says: "The new form must be within one size category of your normal size.". Polymorph is as per alter self with noted changes... the noted changes don't override the referenced text from alter self, they just add an additional qualification for not polymorphing the target smaller than fine. So no polymorphing to tiny size from medium.
Additionally air elementals are roughly humanoid in stance (ie walk upright, not on all fours/sixes/eights/whatevers) so to serve as a mount it would need to be two size categories larger than you (see recent threads about goblins mounted on ogres, among others). So you'd need to be tiny, and then you'd need to enlarge your familiar to medium. Or you small, and it large. Either way, you'd need an alter self/polymorph followed by a reduce/enlarge on one party, and a enlarge/reduce on the other.
Or your 'greater reduce' + enlarge / 'greater enlarge' + reduce.
Well, that kind of puts a damper on it a bit. What is the difference of "serve as a mount" and just carrying me around? I was thinking of making a Exotic Military Saddle with a Lighten Load command, usable 2x per day. That way, he wouldn't be that weighted down. Especially if I'm 1'3" and 22 lbs (Reduce Person is half, greater is half again). Seeing as my air elemental can only carry 24.75 lbs or less in light encumberance, he would be almost to medium by carrying me.
BTW, I found the Lighten Load spell here: http://boards1.wizards.com/archive/index.php/t-328077.html. Is there a better spell than this? Or a more legit one?
Thanks for all the help!