A dual wall pipe, if done right, is much less heavy than the insulation blanket alone. Just so long as there is a bit of air coursing over the outer wall of the pipe, that should be enough to protect the fuse. There are insluations out there that are better than that blanket crap too, much lighter also, made from kevlar weave and aluminum foil. Heck I think even triple wall is lighter than that ceramic blanket stuff.

I know Tam is the expert, but I mess around with this stuff for turbine heli's. We don't get the inflight cooling that you guys get from forward air movement. Our RPM's are less too tho, it is still hotter than you know what and a PIA to get the heat out of a fuse. The insulation I mention is a Vario product, and you can get it from East Coast Vario .
Jack