I would go with picture #4, the one with just the two guys in the hatches. I think it will be difficult to pose the third guy realistically without some modding. In the first picture, you'll need to carve both his arm and the shoulder of the loader because when someone leans against someone else, the "softness" of flesh and clothing (um, sorry, that doesn't quite sound right on this board, does it?) means the contact point must really fold together closely. As it is, his arm looks unnaturally rigid against the loader's shoulder. The second picture is OK, but as Al said, he looks precariously perched. Plus, his right arm is just sort of hanging out there. Someone in that position would most likely have it braced on top of the hull for stability. And the third one doesn't look right at all. So, I say ditch him or get ready to do some carving.
Just my humble opinion...