I had to cut a hole in mine to do some valve work. I went to a local graphic sign shop and the gave me a large piece of black coroplast (same material they use to make yard signs). I cut the right sized piece I needed to cover my hole with 2" overlap on all 4 sides. I used 1/2 self tapping screws to secure the new piece in place then sealed the edges with gorilla tape. It has held for 2 years now.
I can also remove it is needed to service my valves in the future without cutting and then can replace as needed.
Steve Rinker
Rochester, NY
2013 Keystone Sydney 340FBH 5th Wheel, 12,280 lbs loaded (scale)
2015.5 GMC Sierra Denali 3500, SRW, Duramax, CC, Payload 3,700 (sticker- not scaled yet)
Take my posts for what they are, opinions based on my own experiences.