I've got a supertrap on my HPC. It's fitted with a 5'' diameter silencer and belts out about 105dB. In order to fit the trap I had to cut the lip off the pipe and weld on one of those steel end pipes that make the tailpipes of cortinas and things look nice! I then used a thin sheet wrapped around the trap and pipe and jubilee clipped it at both ends. Bit of a mess but it seems to be the most cost effective way around the noise problem.
First time out I used 8 plates which got me down to the required 98dB static at Goodwood (just). However I got nabbed coming past the pits over the 96dB driveby. I then went down down to 5 plates and was still at 98dB (surprisingly) but this time learnt to change gear at the exact point where the man with the gun was standing!
Saying that, with these few plates, the top end was shot to pieces.
