Bob,

I don't think a full length pipe will create such a large gain over the JettStream muffler, on the low load props recommended by Jett (10x6 APC) for the .50.

Dub Jet writes in his web site, that since the JettStream is already a tuned exhaust, the boost afforded by the full length pipe will be 200-300 RPM. Maybe not enough to justify the added weight and cumbersome size, compared with the JettStream.

If you use larger props, which run at a lower RPM level, for which the JettStream is out-of-tune, you could adjust their length to get a boost of close to 2,000 RPM, over the JettStream.

Clarence Lee made the same observation, testing MVVS .61 and .77 engines, in RCM. But in this case, both the full length pipe and the tuned silencer are made to be effective in the same RPM range. So the small 200-300 RPM gain stays.