If you have Cyradon, you could maybe get by using the Gryphon charts.
Otherwise, use your best judgment...
I don't think it would be really similar, you know... Gryphons do fly. I have the Cyradon but i didn't really like the world itself so i didn't even though about look for any info in there. I will when i get home. Maybe worth the shot.
Couldn't you just use the BMR of horses?
That was my first thought to be honest. It would be something between 16 and 20, according to different horse types, than i thought it was just to wide to represent and, unfair with the other players that roll random heights and that are directly linked to their BMR.
So i came with something like that, I've dug my old Rolemaster material and got the Centaur height at 6'6" and 7'4", I'm used to metric system but, if not mistaken, would be result a base (medium) height of 6'11". which would give him 12 BMR + Qu Mod. Since their also Quadrupeds i though about doubling the Qu BMR bonus.
I fact i think that might work but before state that as a rule, i came check if someone would have a better idea, a chart elsewhere i could have missed when passed my eyes over the books or even an "official ruling" for that.
I have a set of custom rules which handles all forms of BMR - it is used for creatures but will work in your case.
You can download it here -> Creature Rules
I've checked your post, seems to me you have a lot of work to come up with that material, i could check if it work for me but than i realized that i don't know the BL of a centaur just their Height.
Thank you all for sharing your thoughts. =D
