The piston has an anti rotation pin. The ring climbs up the pin and it wears out the ends of the ring real quick. I don't remember if I removed the pin or just drove it in all the way but it's unnecessary and needs to be gone.
I did a test. My Brodak 40, factory muffler (with .360 restrictor insert) turned 12,800 and is 240 Grams. The Webra turned an 11-4 at 12,400 rpm and is 330 grams with muffler (factory muffler is very light). So, a bit less power and 3+ oz. heavier.
MM