ORIGINAL: B.L.E.
I'm sure that a smaller 1.2 FS or .90 two stroke would be adequate for sport plane use, but if you are competing, you better use what your competition uses. There is a tendency in competition, not just F3A, to blame the equipment though. A thousand buck investment in practice time, fuel, and possibly even a good coach, will do most people a lot more good than trading in last year's equipment in for the latest and greatest.
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I haven't seen a 26cc gas engine that can keep up with a strong glow .90 two-stroke or 1.10 - 1.25 four-stroke. Of course, I haven't experienced that little 3W engine that folks rave about. Maybe that one could keep up.
I'm with you on the practice being by far more important than the equipment, as long as the equipment functions reliably.
A good coach can be very difficult to find. I had two terrific coaches when starting out in pattern - but not much money and not much time when working as a Draftsman in the day time and a musician during the evenings. Plus, while I can build a flyable sport or fun fly plane, I do not build well enough to produce truly competitive pattern aircraft. Hey, you can't do everything well...<G>
Ed Cregger