Please don’t. There are multiple solutions that are better than what you’re suggesting. Not that it won’t work, it’s just a poor solution to your issue.
Also not advisable for resale. If you were to sell it to anyone who saw and understood that, it would either make them walk away or at least really wonder what other weird jethro engineering was hiding in the camper.
Yikes.
This is the way manufacturer's with perimeter frame construction do (did?) it when you ordered it with a riser from the factory. I've been using a rubber mat with my camper and when I removed the access panels to look around I noticed one of the cross pieces for the access panels had been pushed up. I suspect this is due to the rubber compressing around the loading points causing an upward pressure in areas that weren't designed to take loading.
There are a multitude of screws that secure the access panels to the bottom of the camper. I'm just be putting some additional screws between the existing screws to secure the 2x4s to the camper. If I remove the 2x4s I can just put some more screws in the holes to have some more screws securing the access panels. I also used some L brackets connected to the 2x4s to locate a 2x6 underneath the fresh water tank so any loads that make it through the insulation will be transferred to the truck bed.
