RE: muffler for Thunder Tiger .61
John, If you like quiet, then go electric (YUCK!!) or fly sailplanes. I have a number of 2 strokes with Bison and Slimline pitts mufflers and A) like the sound, and B) have had no problums with them. Never had to plug one pipe to get fuel tank pressure or any other issue that was caused by the muffler. I am using 8 pitts type and 2 sport scale type on O.S. FX, O.S.LA, Super Tiger, and MDS brand engines....ALL GOOD!!