Looks great Ken!!! What kits/parts did you by from USP? The rounded roof ends look cool.
When I put the USP roof on the OKE shell, I ran a couple of lines of super glue the length of the car, lined up the 2 parts, and started putting it in place. I squeegeed it with a roller, put more glue lines down, and repeated the process. Make sure the parts are lined up at the beginning. Wish I could think of something else besides super glue. We're talking of a piece of thin styrene almost 6" wide and 20"+ long, not easy keeping things square.