Updating and renaming the topic.
I tried something else : duplicating models and deleting all unneeded polys. I finallly have all my parts on one skeleton, but animations are chaotic.
Models look good in 3DS, but are totally bugged once exported in M3 (cf preview in SC2 editor as attachement).
Can someone explain me how to fix it ? I still have this kind of glitches when processing a model without splitting it in several parts.