It could be anything really, (without seeing the model I can't be sure) but start out by making sure the hands tags (*l_hand and *r_hand) are in the model. You should also see an error message in game when you select your model, this will help to determine the problem.
Scerendo's Poe Dameron would be a good flight suit (it would need to be edited bigger) and MB2 has a Porkins model, but honestly I would just use a standard bearded head, texture it, add hair and make it rounder.
Personal preference, really the only reason. Feel free to add the ported head on.
https://www.dropbox.com/s/ea7ec3gxel761pv/Dryden Vos' Blades.pk3?dl=0
Small pack to kick off 2020. Battle droid from the original BF2 and Dark Ritual Dooku.
https://www.dropbox.com/s/1twltwqfl8d110f/New Years Pack.zip?dl=0