minerick, a dealer installed three steel angle beams from one frame rail to the other to stop tank sag. They were screwed in the frame and were under the coreplast. This was on warrantee. I can't comment on the repair, because 75 miles later an axle locked up and we crashed the entire rig. It was an Arctic Fox 25R brand new. YeeHaw!
As a former resident of Truckee, I know how cold it gets. Are you trying to insulate the camper for winter usage or do you intend to tow it after the mods? If you're intending to park it for winter, you might consider the moisture element also. Propane heaters and stoves put out lots of dampness.
