Headhacks models...

Hi guys i know it’s maybe the wrong section , but i downloaded on gmod.org two headhacks packs. Those are replica head hacks models and crysis head hacks models… But when i spawn these, they fly everywhere on the map, making my game lagging and some polys are going everywhere… How do i fix this? thanks

Ps; it has been already demanded, but is iot possible to headhack the old Halo 1 marines? thx