I see, power will not be the issue, as the four strokes are not affected by the supercharging effects of pipes as the bouncing shock wave will find the exaust valve closed, so maybe noise could be the main difference, but the longer pipe, I think, it will make the engine run cooler, as all the hot gasses has more are to dissipate heat on the longer muffler.

I personally feel the engine at full power discharges a lot gases/pressure, on my install I see the pipe moving back on the header around 1/4", but I also understand the fact you dont want to open the fuselage.

I hope you don't mind me asking, but I see you have two aligned bolts to support the landing gears, am I correct?

Regards