Armored_Sheep (BIS dev): It is a matter of animated skeleton bones hierarchy. In OFP the selections overlaped, to build dependency. In ArmA skeleton is defined in model.cfg, so selection of bones don't overlap. http://community.bistudio.com/wiki/Model_Config#cfgSkeletons

ShadowVolume

ArmA/OFPE only: Visible shadow resolution lod for model. Typically named ShadowVolume 0.000 (Few features) and ShadowVolume 0.100 (same ammount of features as the main visual model (i.e. equipment, weapon systems, etc). Structure within it must be Triangulated and have Sharp edges. (Also see Shadows)