the cost is fairly high compared to plywood. A 6000 X 2500 mm sheet is around AUD$1500 for 25mm thickness. This is fairly expensive.
The upside is it seems fairly easy to work with and the guys at the factory have offered there full support to trouble shoot the build
I cant help but think that is I use 3/4" ply and route out a skeleton and fill with light weight insulation that I can keep the weight to a minimal ( and the cost) Paul.
One of my stumbling blocks here in Perth is that I have never seen a TD on the road to help in my R and D!!!