I decided that for cool weather camping that adding some insulation to the floor would be very nice. Standing on the linoleum-on-wood floor in my socks when temps were in the 40's convinced me of that.
At Lowes I picked up 12 feet of grey anti-fatigue mat. This mat is 3 feet wide. It turns out that the center aisle floor of my A-128 is just a shade narrower than that. In fact, with the cabinets poking into the aisle or not by one to two inches, with just a little trimming in the right places I got a darn-nice fit. The longitudinal ridges on the mat allow you to make some nice, accurate long cuts with a sharp knife, by following a ridge.
I had to add a second separate piece to take care of the doorway entrance. I was a little worried that the mat might get in the way of opening the refrigerator door. The mat is 3/8" thick. No problem! The door clears nicely.
The mat is a little like memory foam, in that it will take an impression of any weight that sits on it, then it slowly pops back when the weight is removed. I guess that means it has a lot of small air pockets in it which should make it a good insulator.