After reading through his site a bit, it seems he has some problems with water infiltration. I am not surprised, as there is little support where the "holes" in the honeycomb are. It seems a toe would dig in and cause a stress fracture there, and then you're in trouble! He seems to think it was just a flaw in the cloth. Who knows? I wonder if you could do the same construction using very thin balsa instead of cardboard. At least then if it got wet it wouldn't lose it's structural rigidity, but would it weigh more? I guess one could weigh a sheet of thin balsa ply and compare it to the weight of cardboard. Probably a bit heavier I would guess, depending on the thickness of either material, and how many layers ply, and blah, blah, blah...