That's exactly what it's like, the big challenge is doing it vertically. If you could lay the camper on its side it would be easy. The secret is to over cut the filon and then trim. I aligned the top edge so it would run straight, then everything else gets trimmed. The window and cut outs started as a 1" hole in the middle of the opening. I drill those on the ground with a backer board. Once the filon is up, then I use the router with a flush trim bit to follow the outline of the opening. This is the same process that I used with the luan.
I rough cut the filon under the cabover about 1" long/wide, so the piece would be lighter and have room to trim. You would never get it to line up on multiple edges when installing.
The trimming doesn't have to exact since every corner gets a trim piece and I plan on wrapping the top seams in 4" Eternabond tape.
