No doubt the best 26GT performance comes with the tuned pipe...especially with the Ed Skorepa's ES Cmposites carbon pipe saving 4 ozs. But, if not the tuned pipe then what muffler? Be specific to make and model number. Also, any ideas for an offset header that pulls the pipe back into centerline? Thanks.

This engine has a score of muffler solutions ranging from:
3298 - leaky side muffler, steel, very small, very low power. Can be adapted easily
3270 - side muffler, 3-chamber alu, reasonable power and muffling.
MTW 30, small canister muffler
MTW 40, larger canister muffler

These MTW mufflers are in my test program. This is time consuming, so please allow me some time to publish the results.
The larger engines perform very well using the MTW design. So far I am confident they are the best value for the spent money, both in the power, and in the muffling properties.

SS header, 22mm dia, offset 90mm or 50mm, 300mm long. Rolled solder-on end pieces soon.
Stainless steel DIY header sets are available, which allow the pipe to return to engine centerline, as well as height adjustments.
Shortly, still hush design headers will be available for ultimate flexibility in plane setup.
Wall thickness is 0.5mm, so these headers are very light and durable.

I also got the inverted pitts and inverted muffler for the 26gt. My plane has the inverted muffler on it from brisson becuase it fits in the cowl for my application better. If you would like to get a $100.00 inverted pitts for pretty cheap that still NIB let me know, I don't need mine mine. Brisson said they both will produce the same amount of power (when compared to each other) but make sure you cut the turned in tips off the pipes.

Does the Evolution 26GT and 35GT share the same muffler bolt hole spacing?. Is the Bisson "Pitts" style muffler the same volumn muffler for both the 26GT and the 35GT?

I trying to identify the model number for largest volumn Brisson "Pitts" for the 26GT.

Bolt spacing and port sizes are not the same, look up at http://krumscheid-metallwaren.de