ORIGINAL: panhndl
Sounds like Zenoah is the best option. Now...45 or 62. I don't think that I'd worry about the weight shaved by losing the magneto, especially if the magneto meant increased reliability. Also, with the 62 only weighing a few onces more than the 45, is there any real downside to running a 62 other than maybe too much power for that small a model?
Being a larger engine, there will be a bit more vibration with the 62 compared to the 45 but certainly not excessive. Either engine converted to EI will idle smoother and start easier than the mag version. Great engines in any configuration though.