I find that the manufacturer's recommended engine range doesn't usually give me the performance I'm looking for. I want to know what size 2 stroke engine will give me excellent 3d performance and unlimited vertical. My plane is a 67" yak that should weigh around 10 lbs. The manufacturer suggests between a .61-.91. From past experience, I know this won't do the job. I don't want to go 4 stroke, so please don't tell me that.