I tached my 53 yesterday at the flying field, testing funfly props. 70 degree day, Morgans Omega 5% fuel, and a 3 yr old Enya No. 4 glow plug. I use a Macs one-piece muffler, which is not supposed to give a performance gain.

APC 11.5 x 4 (was originally a 12x4) - 14.9 k

Grish Tornado Magnum 12x4 wideblade new - 13.2 k

needle was set for flying. Not peaked right out.