The mdl's in the next AD patch release will have the onseam values fixed, and also the frame mins/maxs (which were all set to 0 0 0, which messes up mdl culling a bit.)
AFAIK, the invalid onseam value (1) were written by Preach's fbx2mdl tool, I think he's aware of the problem though.
Anyway, sorry for hijacking the thread