Bigbird, simply angling the exhaust port of the cylinders back at a 45 degree angle would do wonders for EVERY plane out there, when it comes to exhaust installation. On a warbird with a narrow cowl it would easily allow a short pipe to an in-the-fuselage muffler setup, and an in-line twin would merely route the front header around the rear cylinder. There could even be functional "Stacks" on the side of the cowl, especially of the exhausts were on opposite sides of the engine.

No one seems to consider this when manufacturing engines. A 45 degree angled back cylinder could potentially have better flow into the intake ports as well, resulting in better power.

As for a "IMAC" style plane bias, these are the majority of planes that flat-twins are installed in, and also the largest segment of the flying public that have noise problems.

When the manufacturers STOP making the noise, silly, and totally archaic "cans" a lot of people now use, THEN somebody will finally knuckle down and get on the ball with quieter and better exhaust systems. The handwriting has been on the walls for a long time, that these exhausts are NOT a good idea. . both from a noise standpoint, and how much of a "public nuisance" problem they present to those who are not modellers. I give it 3-5 years before the old style "cans" are basically legislated out of existence from European-like niose restrictions.

What will you do THEN?? Complaining will be WAYYY too late, and those of us who have been pushing the envelope in this area will still be flying. ALL my planes are at 90-91 dB at 25', and about 96 at 9'. That's still too noisey, IMHO, and I have yet to see a warbird or "sport" gasser that was quieter.