I use Saito and have never had a problem with them. If I could afford it all my smaller planes would run Saito's.

As for power to weight the glow motors will put out motor power for the same displacement however by the time you include engine, muffler, extra battery and switch the weight really adds up fast for a gasser. Don't get me wrong I love my gasser but I wouldn't try to use gas on anything smaller than a 40cc unless I just wanted something to putt around in the sky.

I've heard great things about the RCS140 and if I were to try a small gasser I would buy that over a Zenoah any day. I've heard it will pull a 10-12 lb airplane easy but if the wing loading is so high you loose performance you won't be happy.