a couple of things.

from the advanced race guide assimars have a favored class boost that can give an eidolon DR/evil thought it would be worth a mention to put in the guide.

also a rather odd question, if you have an eidolon with anything except the biped base form and you give it arms, presumably turning it into a tauric creature, what size weapons, assuming it is wielding a manufactured weapon, does it use? the reason i ask is because a centaur is a large creature but uses medium sized weapons because the human torso bit is medium sized, same with a lillend, large creature, medium weapons because the humanoid bit is medium.

just a thought.