Your right on the most complete construction diary, I could not find one that is this detailed. The only company I could find that at least has a online factory tour is Monaco Coach and they leave allot to the imagination on their building process. I am not sure why other companies do not detail the process, and even more surprising is customers do not demand it. I was one of those people a few years back. I bought my Coachmen motorhome with next to no knowledge of its construction or make-up. I bought it based on price, fit my needs, and looked nice. And this was even after owning an older Winnebago which I did a ton of updates on and really learned allot about motorhome construction. The funny thing was I did not apply that to my next purchase. But ownership the second time around was the charm, it really set in when I realized I had a rubber roof on that motorhome. I personally do not think a rubber roof is a acceptable solution for motorhome roofs. I know they work if all is right, but it does not take much for a rip from a passing tree branch and cleaning is a nightmare.
As for Show Hauler doing just the box, they do not do this. Show Hauler has worked hard to develop their name in the industry as the best in quality and construction. If they have a bunch of conversions out that have owner installed interiors they do not have control of that quality. I looked into this myself in the beginning and you are not going to save as much as you might think.
This is a very thin product with basically a bubble wrap sandwiched between reflective heat foil on either side. It is used in applications where you will be furring out the wall, which is what Show Hauler does. So they have the aluminum skin, 1" space for steel frame, 5/16" OSB, bubble foil insulation (R value of 5 to 10 depending on how it is used)1"x2" furring and finally the interior panels. So this is one heck of a wall & ceiling structure and I am sure a pretty high overall R value.
2003 28' Show Hauler Motorhome on a 1995 FL 120 completely refurbished chassis. Currently in production - scheduled completion 1/10/03 www.showhauler.com