After looking at the Adult Gohan model indepth by decompiling it with Milkshape 3D (I attempted to make my own model by editing it), I see what's wrong with it. The thing is full of holes. The lower body and the upper torso are connected badly with a piece that looks like it was just cut and pasted there. The lower torso is hardly connected to the body, and doesn't look natural. It looks like you really don't even need that piece. It doesn't look right, and it has holes in it. The body also looks like it was cut in half, because it isn't connected. If you look under the armpits, there is a vertical slit through the body.
The head isn't connected to the body very well. The neck isn't fully connected to the rest of the body. It has holes in it. A panel in the top of the back isn't connected very well either. The model pretty much looks like swiss cheese. It was just cut and pasted together with glue and scotch tape. You should have used duct tape. Duct tape fixes EVERYTHING!