I guess my answer would be use my max plugin which has been recently updated ( There is no right answer for which axis is up as its just a convention. Max uses Z-up by default but can be changed if you really want. So just apply a rotation matrix to suit your needs. My experience with some skeletons is they were reusing bone names or not supplying names at all. I changed this plugin to ignore this on skeleton import (but still used for when merging meshes with skeletons because the skin modifiers really need it). And I had no end of trouble trying to match skeleton and bones. I ended up just hiding the bone mesh and showing the links instead (they dont really matter in the end).