I would like to have a warmer TC floor... any ideas?

sleepy, on my Lance there is an open air channel from the waste valve hatch up under the shower pan and into the basement. I used to have the same issues. First I sealed up any air gaps in the valve compartment walls to the exterior. Then I lined the box with fiberglass insulation and finally I put a bat of R9 just behind the hatch door. no more cold floor.

I have a 04 Silverado with Linex spray bed liner with a rubber mat sense the truck and camper were new, absolutely no rust. The 1161 rarely comes off the truck and has been garaged when not in use which is not often. As far as insulation with this set up not sure because have always used it this way. When we winter travel I usually put the carpet in, have stayed warm in 0* weather.

Your camper has a basement, doesn't it? In that case I doubt any insulation below the lower floor will do much.

Having said that... we have made very good experience (and not even intentionally) with 2" xps foam (goes by the brand name Styrodur over here) underneath the camper floor in our old Lance 915. We needed to rise the camper to clear the tailgate opening of our Silverado and put it on the foam boards. We built a simple wood frame with the same dimensions as the camper floor, filled it in with closed cell foam boards, and hung it from the camper floor. It made a noticeable difference as far as floor insulation goes - no wonder as it basically doubled floor thickness.

Do not use open cell foam as Styrofoam as it will draw and retain water.

In a basement camper I would probably try to put in carpeting against the cold.