I use 10% on my V60 and 22% oil, half and half. 5% works very well, too. Up to 20% when hot at a contest.
I bump start mine, once it's broken in it'll behave. I've flown them mostly in Stunt, so have never used a starter on one. I have one in an R/C model, Sterling P-63 King Cobra, not finished yet but can't wait to try it on the Semco muffler.
Chris...