I wished I'd read the installation instructions for the bottom cowing BEFORE I installed the top cowling. The same trick you use for the bottom would have worked for the top.
You start by marking the fuselage, then transfering the cut line to the cowling. On the bottom piece, you mark the very bottom and up the side a bit, make the cut, reinstall the cowling and mark the rest of the cowling. This allows the cowling to be sitting in the correct position for the side cut. (It will tilt forward a bit after making the bottom cut.)
The top fuselage had the same problem... and this would have worked.
I used a ratcheting strap to hold everything in place. (The strap kept sliding off the cowling, so I used duct tape to hold it in place. I ran the duct tape down the side of the fuselage, then made a pocket for the strap to go through.
