I like the four strokes. One reason is the extra grunt you can get from a botched landing or so on. On my dearly departed minnow the OS 91 pulled me out of a few bad situations by just nailing the throttle. The new minnow is getting the YS 110. Of course Im not into the super high rpm speedsters either. Its a trade-off. I wouldnt say I had any more problems tuning the 46fx over the 91 4c. Just keep the rpms in the specified range and dont let the valves float. Just like a car, overevving is hard on the valvetrain. By recommendations in the speed forum I went with the YS and hynes mount. Hopefully Ill have something in the air by the end of this month.