Quetico Bill - The test used 1.5" EPS foam. That's the cheaper, crumbly white stuff with foil on one side. I dont have 150 or 250 available at the big box stores in California.
The glue job on the beam was very sloppy. I think if I had done a better job spreading the GG and clamping it properly it would have been stronger.
Ultimately I would like to build a 4' x 8' vacuum press from the plans available here
http://www.joewoodworker.com/veneering/welcome.htm and glue up entire panels.
This is getting far from the tried and true method of slapping some titebond/canvas on the foam, but I am dying to see a SuperXL tiny house foamie. Something like this 16' tiny house
http://rockymountaintinyhouses.com/plans/boulder/ but build like a foamie to be a featherweight. What do you think? could you build something that size (maybe without the loft) on a 16' single axle trailer? Do you think you could come in under 3,000 lb?