Brian Yak Dude
50cc
As for the counter rotating, it is really preference. Some people like having no p-factor to compensate for, even though it may increase weight. It is a very careful balance to meet weight requirements while still getting optimum performance.
Maybe [MENTION=413]Brian Yak Dude[/MENTION] can comment in this.
The contra is kind of a gray area for us in pattern, with the majority of electric pilots not running one. For the weight, expense and just simply having another part to break, the contra doesn't really tickle our fancy. There are a few who claim the contra gives them a serious advantage, but the fact is there's no REAL facts on the actual gains of the setup. Sounds all very fabulous in theory, but in practice it's not quite so clear.
The majority of electric pattern flyers (including myself) prefer a good motor and a lite (falcon or APC) prop. although this is pretty standard, it's very easy to get a nice throttle curve and good power throughout the whole flight that's consistent and quiet.
On the idea of bipes, this is also a bit of a grey area. Designing a biplane requires much more effort and determination than an equal mono. Unfortunately in the majority of biplanes in the pattern world, they aren't all what they crack up to be. On the other hand, especially in todays sequences (our FAI F3A) are very demanding on the aircraft, and the WELL setup biplane is seeming like the way to go. They just handle the maneuvers with more aggression and let you command them. But without a proper setup, a biplane will restrict any pilot more than any other plane will.