Scarecrow, Interesting that you mention that, a very good point. I had this originally planned with some friends coming around to help. When I found out the forecast temp was going to be 37 deg C I became concerned re thermal runnaway and I put it off until I got a day in the low 20s. Then still used slow hardener and only 2 layers of glass. Once the frame is built around this skin I'll do a bit more possibly with a 5mm core cell as core, I have a heap of this 5mm M80 foam. I have no other immediate use for it, picked it up super cheap many years ago.