[MAStuart]

I am not sure how a csx 4000 is done. But it would not hurt to glass the skin to the flashing. See if you can find some pictures of how an original aluminum car door skin were installed. They were wrapped around the tube at the top and rivetted to it . The sides and bottom were crimped on like most normal car door skins are installed. To do that is why you have to attach the flashing around the sides and bottom of the tube frame. The flashing is rivetted to the steel tubing frame. You will be doing the same thing. But instead of crimping the skin on you will be using glue or fiber glass. You will also have to make sure the Tube frame is the right shape.
Get started by seeing if you can get the skin over the top tube.