On the track noise testing thing, Chris, I thought the distance was 1 metre not 0.5 metres, but I could be wrong on that as haven't been static tested for a while now. Mick has made me a super set of megaphones which clearly won't pass any noise test on the planet, but I am keen to try them at least once somewhere (where accepted) 'cos they sound flipping fantatsic! I wonder what level they would test at? It would fun to measure them one day.
Last time we were at Goodwood for a sprint, the static noise test was definitely at 0.5 metres and max 105db. Re your megaphones, there was no noise test at the Brighton Speed Trials last year although they said in the regs that you shouldn't be more than 105db I think. There were some very noisy cars and bikes there and no one seemed to complain!
In my experiance the best heat sheilds have an air gap between the sheild and the area you are trying to protect.
It only needs 3/4 to 1" ,this allows the air to flow between the two,the foils are good but not as good as a sheild with foil.
The foils reflect but you would think there has to be a point that the heat will transfere because it is attached to whatever you are trying to protect.
Air gaps is the trick.