I had some stuff that I thought was ready to upload until I found a weird mesh thing while testing. It has to be the trousers rather than the top, because it happens with different tops. The skintight top just has a funny hump at the waist, but the other top actually lets you see the blue carpet through it. The hump/see-through isn't there if they're standing up straight.
It's just a matter of tweaking the bone assignments a little. Find one of the ingame tops and make sure the vertices around the edges of the pants align with the top. Then make sure they share the same bone assignments. For the little bit poking out, it's the same - probably a vertex with slightly off bone assignments.