I spoke to that Cool Carb guy at length at Carlisle last year. Turns out that he makes these out of "end of run" material which he buys for a song. I got the impression that the whole business was built on the premise of "what can I make with this stuff?" as opposed to "what would make a good carb heat shield?". After reading the posts I think I'll stick with a phenolic spacer if I need one.