RE: Four Strokes and Sport Flying
I love 4strokes, but not their prices. The diminutive muffler is a big advantage in scale birds with tight cowls. Often times, if you figure the cost of an aftermarket Pitts muffler to get the 2stroker to fit. the overal cost can get to be almost as much as a 4stroke. However, for a sport plane, particularly an open engine bay (no cowl) like the 4*, the 2 stroke expansion chamber muffler has plenty of room to hang out. To me, the simplicity of a 2stroker fits the spirit of the sport plane much better.
My 4*60 has been flying superbly with an MDS .78 and the OEM muffler. The yet to be covered kit-built 4*120 will receive an ST2300 with OEM muffler.
On larger scale ships the cost differential can be quite staggering. I got a Lanier Extra 300 1.20 ARF back on a trade-in. The previous owner put a Saito 1.80GK on it and had 3D power up the Wazoo. However, the lightweight Saito made the Extra 1.20 a bit tail heavy and he had to put a big ol' Sub"C" battery pack above the fuel tank to balance. I am in the process of replacing the Saito 180 with one of the MDS 1.48s I got dirt cheap after Horizon dumped the line. The little bit of extra noseweight is actually an advantage for balancing. The MDS 1.48 will still have plenty of power for Sport Flying while costing almost 1/3 the Saito 1.80GK.
That said, I just bought a TT .91 4stroke mostly because my 4stroke fleet was getting kinda thin. It will be perfect in a 60-90 size scale bird.