RE: Engine For Kwik FLi Mk. III
you can't really bang the cost of batteries. Noticed the price of glo fuel lately. I am using a 3350 3S pack in an ugly stick (Great Planes ARF with the suggested Rim Fire Outrunner) and I love flying it. No fuel costs and when the batteries give out, the cost will be very small compared to what I would spent for fuel.
John (electric convert)