Dave,
On my first PC I noticed how warm it got in the two storage areas above the driver and passenger. So I put my hand in behind the wall board and found no insulation, just the outside fiberglass and it was hot with the sun beating on it. On my subsequent PC purchases (first 2552 and now the 2551) I requested PC to install insulation in that area. For some reason they do not install insulation in that area, I believe just to be an oversight that no one follows up on. You can get some insulation and force it in that area without too much trouble. It really helps to keep the heat from baking those areas.
Before it is asked, the reason we went from the first 2552, specifically made for us, to a 2551, was the gas mileage. We were averaging 5.3 mpg on the 2552. The Ford Dealer said that was very bad but they could not find anything wrong with the engine. Could not afford to drive a lot at that mileage. Our Roadtrek 210 tripled that mileage but wife wanted more room, so back to a 2551 and its mileage doubled the 2552, so there was something wrong with that engine. We average between 9 and 10.5 mpg, not good but acceptable compared to the 5.3. Those that claim 12+ mpg must have very good engines as I can only get 12 on the flats, with a tailwind and below 55 mph and I do not tow.
Bob