Actually, what many people don't realize is that the 1966 OS Max .10R/C is a very good upgrade for a large .049 airplane. It only weighs 3.1 ounces. The exhaust baffle restrictor plate provides a reliable idle and it can idle for extended times, then power back up smoothly. At idle to half throttle, it sounds muffled. At full throttle, it puts out the noise of an unmuffled .049 reed valve engine.
It would be good for something like Ken Willard's 39 inch (991 mm) wingspan Top Flite Schoolmaster. On mine at half throttle using a 7x4 prop, it flew very .049 like, but open it up and it scooted along quite nicely, just like a lot of larger airplanes. It would work also on Hobby Shack's 46 inch (1168 mm) wingspan The Real Thing. A 2 ounce fuel tank is all that is needed for decent flight duration.