Hi Jay and Alice,
It looks like an awesome project. I want to comment on your choice of alucobond for the skin of your camper. I am a sheetmetal worker of 30+ years and have used alucobond quite a bit. In fact I used it extensively on the interior of my custom popup camper on my Toyota. And I am using it on the camper I am building now for my 3/4 ton 4wd Dodge. I would like to detail what I know of the product.
The pluses are:
It is extremely rigid, does not distort like most materials, is moderate in weight, and has an incredible color palate.
The minuses are and this is why I wrote you)
The material dings easily. The core is fairly soft, and the skin is .030. If you have not done this already, obtain a piece of it, and whack it lightly with a hard object. That is my only complaint of this otherwise awesome material. Either the 3mm or the 4mm would be a good choice. Also I wouldn't go with the metallic colors, they don't touch up well. You probably already know all this, but I know (from being in the middle of a camper myself) that there are so many decisions to make!