The only problem I got with single cylinder 4 strokes is that they are such vibrators... Two strokes just aren't as bad, having twice as many power pulses.

Have you ever watched the control surfaces of a big (okay, medium sized) 3-D model twitch when its Saito 200 is idling? That's hard on all the rigging, joints, radio and everything else.

And for this reason, I like to use twins, preferably the ones that have both cylinders going out and in at the same time; in other words, with two opposing crank pins, not just one crank pin.

The single crank pin models are mostly the older Saito medium to small sized twins.

You can tell which ones have opposing crank pins if you notice that one cylinder will be slightly ahead of the other- they're not perfectly in line (like they are in the sinlge crank pin Saitos).

In these motors, the vibration from the masses of the two pistons going in and out cancel each other out, and they vibrate less... which is a good thing.

Same thing goes for Gas motors, as well: more cylinders are better.