I find myself operating with sheer guesswork in my efforts to offset the effects of flying at the altitudes I live and (fly) in. Can you supply some data which gives me more to go on in making the proper compensation in engine size for altitude? I usually fly at about 5,000 feet elevation. My engines are all OS 2 stroke of various sizes. Thanks, Blue

We don't know if there's any real data. Most modelers go up one engine size at about 3,000-5,000 feet. Some models will fly just fine on their originally-specified engine...varies.

Thanks Bax, That's what I've been doing and will continue along with the rest. Appreciate the response!