Here's a Pup built by Howard Henderson showing his solution. I searched under "Sopwith Pup" and found a site by a fellow named "Martin" that has walk-around photos of a real Pup but they're well protected. There is one close up of a clear inspection port that shows the details of the panel screws and plastic overlap.

http://www.ivyandmartin.demon.co.uk/.../pup_n6181.htm