I am just breaking in a Tower .75. Had fuel draw problems with my fancy dual tank system for the first 12 oz or so of fuel, couldn't get it above 8,000 rpm. Switched to a single tank with simpler plumbing, got it over 12000 on a stock (not balanced) APC 12x7 with K&B L-1 plug and 15% nitro/20% lube, with plenty of exhaust trail visible. After about a minute at that rpm the muffler blew off its end cap and for a few seconds I had maybe 18000 rpm and a mighty roar. I found the end cap about 20 yards away, put it back on with a nylon lock nut, started up and again went to max throttle. Within another minute the muffler blew again, this time the center rod stripped the threads out of the muffler's aluminum front bell. Same big noise, didn't scare me so much this time.

I have run a #6 threaded rod through the muffler, put lock washers, jam nuts and thread lock on both ends, and will take it out today with a balanced 13x6 Zinger and tune the low end.

No question this is a very strong engine, ample power for my .60 Stinger, so I will not be pushing the limit on rpm at all. The plane is under 8 lbs dry, just over 8 lbs with 12 oz of fuel, and the Zinger will give me close to 10 lbs of vertical at even 11000 rpm, which I expect will be no problem.

As to comparisons with other .75 size two-strokes, I have a GMS .76 which is a comparably strong performer although I haven't tached it lately, and an MVVS .77 which turns in the 12's on a Zinger 12x8 with 10% nitro.