True, it is arbitrary and inaccurate to use a d20, but that's what we've got.
In another thread on this topic (there have been a few) Someone suggested making attributes out of a 100, and really the higher you go the better. You could also do away with any score modification and only have maxium ability scores, with magic being the only way to exceed them.
Chimpanzee's are lanky too and yet their Strength score is going to be much higher than a human, using the Githyanki can be as much a point in favor as against.
