My setup for the Tower 40 is to B&B the motor. ( balance crank make sure all fits are in specs) Cut heat dam on head, fins, and install either a .255 venturi with OS NVA, or better, a PA NVA with .281 venturi, 1 or 2 head shims, NO change to the Excellent head plug in, fuel with 22 to 24% oil mostly ( 3/4) synthetic oil. Bolly 12 x 4 is best I have ever seen on this, or use a Power Point 11 x 4, Z pro 11 x 4, Cyclone 11 x 4.5 2 blade props, launch in mixture cackling 4-2 or just barley into a 2 stroke, engine will unload within 1 lap and get a little richer, open free flowing tube, or tongue muffler .
some get a 11 x 5 and run a 4/2, DO NOT use as 6 pitch prop with this setup, it will run away , DO NOt use a very restrictive muffler, use whatever nitro you need for the Weather/altitude/humidity
Randy