Dan, Gary and others using a tuned pipe,

More info on the coupler from Rendegade who advised me that the stuff he is using is from Purosil, which is an Aussie supplier. Rendegage said that it lasts about 100 flights, is relatively cheap and easy to replace.

Got the specs on the Purosil silicone tubing (SAE J20 R1) and did some poking around today and found a [link=http://www.siliconehose.com/commerce/ccp11370-870id4-ply-silicone-saej20-compliantgl-c40-087.htm]USA-based supplier[/link] of the material, whose specs are SAE J20 R1, which they refer to as "silicone turbo hose". The 7/8" ID size costs $0.83/inch, and I ordered 18 inches of it to try out.

EDIT: price/unit corrected! Thanks, d bodary...