I have looked at the geometry in Max from x file, MS3D, and FBX.
It appears that when on top and crouching that you are actually standing on the Joystick Deck. Even if you walk off the back it appear to be the same height as the front.
Try changing the collision in the FPE file to 1 - Polygon, then try number 3 Cylindrical and see if any of these inprove the situation.
I have rescaled it up in max a bit to see if that would make a diffence. But it did not. I even collapsed it all into one mesh and it did not help either. I would start with the Joystick deck as your first culprit, as that appears to be the one player is actually standing on.
As I do not have Wings 3d I really cant say, All I see is the results in the game engine. Sorry I could not solve complete.
Try just a square box the same dimension and make a quick FPE file and see if you can even get on top of it. I think you will find you cant. But as you stated earlier, I will just put a black box around it, Just might be the solution unless you want to play with the mesh some more. Sorry
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