This was one of my most successful designs, fitted to a S200. Yes it's ungainly and no it's not very well finished, I couldn't wait to test it.

http://i.imgur.com/73Pqo4l.jpg

It's a reflex design with four chambers. The overall length is close to 200mm and the OD is 60mm. It's a tube within a tube, the inner tube is 50mm diameter. Air passes along the inner tube and through three baffles. Once it arrives at the last chamber it can escape radially through vent holes in the inner tube and then blow back in the annular void space between the two tubes. You can just see the vent holes at the back.