Hey geof, got your emails, still trying to catch up. Doing much better and in a week and half I will be able to sit again.
In regards to insulation, if your going with big R values, don't forget about the windows, if you don't use thermal, than you will loose alot of that savings right there. Also the cab will be a big loser as well, so you will need a insulated curtain to block that area off. And last if you are going with big slide outs, say signora to your saving when you have them extended. The rubber gaskets are good, but don't have great R values.
Bubble insulations use is dependent upon the construction of the coach. If the builder does not use interior sheathing before apply there finish board then a heavier insulation is a must. In Show Haulers case they run 5/16" OSB throughout the entire interior first to build strength in the steel frame and then as a insulating barrier. So the bubble insulation is a second layer used for its insulating properties and a vapor barrier. (not saying it is better or worse just Show Haulers way)
I will say that on my trip to Florida we encountered extreme cold and very hot temps and this rig blows away my previous motorhomes I had as far as how well it held cold or heat.
Paul keep us posted, and I can't wait for some pic's, that truck sounds awesome!
Bill
2003 28' Show Hauler Motorhome on a 1995 FL 120
www.showhauler.com