I have owned several Jaycos and only one had the thermal package. I was surprised when I had to take the coroplast down to do some work in the enclosed area. The underside was enclosed with a solid piece of coroplast from front to back. This is a piece of cardboard looking plastic that is abount 1/8 inch thick. I dont feel it provided much thermal protection. The insulatiion was a piece of fiberglass insulation abount one inch thick that was the size of the bottom of each tank and it was held in place by the coroplast against the bottom of the tank. The heat vent was a pipe about one inch in diameter that came down from one of the heat ducts about the center of the floor form front to back. The charge for all this was $357 on the 2008 Jayco. I dont feel it was worth that much to me and certainly not worth a 6 week wait to get it. JMHO
Regardless of its appearance, do you know how much the thermal package increased the R values?