You are reading my mind! Unfortunately I have no pipe tunnel in my 73'' Pilot RC SBach. It is listed as a feature, but it's not there! I actually had the Syssa and IBEC in my ''cart'' on the website, but baulked. The plane is supposed to be 10.5 lbs...what do you think?
You can run the engine on its included muffler and turn a smaller prop. It would work fine with something like a 17x8-10, 18x6-8 or 19x6 on muffler. Expected rpms in the mid 8's
The pipe allows more pitch to be used. I use a 17x12 apc and have run 18.1x10 apc and 19x10 hybrid that I make myself. All work great on pipe. My rpm is in the low-mid 8's on pipe.
If the plane has no tunnel built-in, then your options may be limited to running muffler alone.
My pattern planes and the 78" EF Extra have superb performance on pipe. Pattern planes are 10.5 lbs and Ef Extra is just under 11.5 lbs. Your Sback weight is on par with these.
The SAP will take 3-4 gallons of regular 87 Octn gas to break in. I use BelRay MC-1 synthetic motorcycle oil at 50:1. Buy at motrcycle shops. SAP recommends the Amsoil Saber Pro synthetic at about 85:1. I've run both and sticking with the BelRay
Before making the jump spend a couple hours perusing through the thread....lots of good info there. Bottom line, it's a great engine and is made here in Conn. Todd Syssa gives great service too.
Good luck and let me know if I can help