Front Cargo Door Warped

2012 Landmark, I installed an Onan 5500 LP generator. I cut out the panels in the floor for the exhaust and air flow. Ran generator for 1hr with the cargo door closed and it warped from the heat. I did this as a test to see who thing would work when traveling down the highway with the generator running to precool the unit. I have friends and I have read a lot of reports that thats what a lot of folks do..The trailer was prewired, gen. stand and cabinet so it's not like I'm putting something where it does'nt belong.

Any thoughts. :h