Jlb, the f-r distance of the BME is right at 6 inches. For exhaust on my two BME Xtremes, I run a 90 degree elbow (25mm OD, from KS, available form DA) and home made flage (though flanges are now available), then couple that directly to either a "L" or "LL" Pefa canister available from Aircraft International. That makes one muffler for one cylinder, so you need two of everything.

Sound signature will depend on how fast you are spinning the prop. . a 28" Mejzlik at 7000 rpm will be 3-4dB louder than a 28" biela or Menz at 6400 rpm, and with the thrust from these props going to the biela or menz is really a better idea. the Mejzlik just spins so fast it stops increasing thrust at some point, so all that rpm is wasted.

As for balancing the plane, my 40% Composite-Arf 330s has NO lead in the nose, the batteries, rudder servos and fuel tank are on the wing tube, and its actually slightly nose heavy. On the 33% CA330 it was difficult to keep the plane NOT nose heavy, and all the servos and batteries are behind the CG in order for it to balance correctly.

All-up weight of a BME Xtreme, shorty headers, "L" canisters and ignition is right at 6 lbs, or slightly lighter than the DA100 or 3W 106 weigh with standard mufflers.