Allright, after searching the forum for "durofoam" I found the following thread:
viewtopic.php?f=277&t=64894&p=949663&hi ... am#p949663
I don't know how I missed it. So, I'm back to the drawing board. I'm going to keep looking, but all of the threads I've read regarding locating R-Max or other Polyisocyanurate based boards in Vancouver/Western Canada have gone cold before anyone mentions if they found a solution. Here are some options off the top of my head:
1. Use durofoam with a wood frame or plywood backing. If the main problem with durofoam is it's lack of rigidity, couldn't I improve the rigidity? Theoretically, I could use a foam-safe adhesive, affix the durofoam to plywood (shiny side out), and tape all the edges with foil tape. Also, to save weight, I could make flat-wise frames for each foam section using 1x4s, pocket screws etc... I know it sounds labour intensive, but I love doing things like this. Furthermore, I'm stubborn. Any thoughts as to whether or not reinforcing durofoam would work or not? I'm not interested in discussing whether or not it's worthwhile... it is to me if it allows me to build a viable structure.
2. Do a run down to the states for R-Max. So far, no Lowe's between Vancouver and Portland seems to have it in stock. Home Depot doesn't seem to have a Polyisocyanurate product anymore... I haven't finished looking though. This would be the easiest option IF I can find R-max... preferably not further than Seattle. Edit: I may have found some R-max at Home Depot in Bellingham.
3. Give up and buy a really nice tent. Now that I've been obsessing about building a hexayurt, this option would feel like giving up. I'm sure a lot of you can understand why this is my least favourite option.
I hope to follow through enough to the degree that I can provide a workable solution for people in my little corner of the world...
Thanks again everybody.