Check back through the magazine, there was an article about a simple pepperpot exhaust I seem to remember.
If you want to quieten the exhaust easily, a simple extension of the pipe with the end closed and multiple holes drilled around the last 4 inches of the pipe works very effectively - A friend had a system fitted to a Reims Rocket so it was CAA approved. Point to note is that the holes you drill must have an area greater than the original exhaust so that flow isn't restricted.
Check Airworld's site, they have a similar silencer.