Being as it appears that I can only get 1" xps anywhere near me, I'm thinking I'll just go with that and face glue them together.
I've done a lot of research and know that foam fusion and Tb2 should both work, but $ wise I want to use TB2. I've seen the results in videos of small samples being face glued. My only concern is if in the middle of the sheets is it going to dry and cure ok? Will I need longer cure time?
I will be prepping the sheets by sanding the surface and perforating and will be doing PMF both interior and exterior of the final doubled up panels.
I'm actually thinking now that possibly only finding 1" is a blessing in disguise as it will be easy to just rip 1" thick wood to use anywhere I need it and plan out the layers, instead of having to cut or route out channels in 2" for wood. I will only be using wood around the perimeter of the base, around windows and doors, and some roof spars.