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.