Sorry about the delay, I just got to updating this now which seems like a shame since it's a relatively minor edit:
His ptera-pectorals look as though they're stretched over his shoulders like a cape. Give them a bit more weight on their own.
Rather I think the problem was that they were in some weird middle ground. I actually made them even
less distinct since in general he has a very thin physique. There's not much muscle there.
He has no hips, the legs are connected to the ribs almost. Hips are supposed to be really pronounced in bipeds, since they're so vital
Made the hips more pronounced. The hips are there in the original, just not very visible.
Haven't decided what to do about general flatness (if it's a problem). Here's progress animation fun:
