Update to this thread, foam has been doing well, no real issues. I had some freeze up issues Christmas of 2023 and temps weren't horrible, maybe -5F. I found that the heat pad for the fresh water tank had stopped working. I dropped the coroplast and inspected everything and what I found disappoints me. For starters, under the drain area of the fresh water tank, the reflective foil barrier was folded out of the way instead of going under the drain portion of the fresh water tank, same for the fiberglass batting in the same area, so basically no insulation under the drain area of the fresh water tank. This allowed the bottom of the freshwater tank to basicly freeze solid! Next I inspected the batt insulation above the rest of the coroplast and what I found was lack of quality control! Over half of the fiberglass batting was short of reaching frame rail to frame rail by 6-8 inches. This basically defeats the purpose of having insulation in the belly and explains why I poured lots of extra heat into the belly and still had freeze ups. I removed all of the batt insulation behind the fresh water tank and reinstalled it correctly. I used a bead of expanding foam between the bottom of the rear most crossmember on the frame and the rear wall to seal off the 3/4 inch gap. Then I ran a full piece of fiberglass insulation up against the rear most crossmember to provide insulation to the rear most section of the belly. Then I cut 12-16 inch long sections of fiberglass to add to the oem batting to make sure it covered frame rail to frame rail. I strung sections of duct tape tied to the crossmember behind the fresh water tank to the rear bumper to hold up the fiberglass batting until the coroplast could be reinstalled. I ordered a Ultra Heat tank heater rated for 75 gallons and it is about double the size of the factory pad. It is also about 160 watts compared to 77 watts for the factory pad. I had to use a heat gun to warm up the glue on the pad as well as the bottom of the water tank because it was only about 20 degrees out when I installed the pad. I unfolded the reflective foil and notched it to fit under and around the fresh water drain and did the same with the fiberglass under water tank. I also used some eterna bond tape to seal the area above the spare tire and also where the coroplast was notched at the rear of the frame. When this latest cold snap breaks, I will take the Solitude out and see how it does, but with temps in the last week at 27 -36 below zero, I will stick to keeping the wood stove cranked up in the house.