I'll never understand the fascination with getting "great fuel economy" on a stunt engine! If you have a OS LA.46 that is using less than four ounces for the pattern, you aren't getting all the available power out of the engine. Yes, you can detune the engine to fit special circumstances but there are other ways to do this than by strangling down the engine. if you need to choke it down that much, you might want to consider a smaller displacement engine. Everything from the engine start, through the flight and shut off is more predictable and consistent, I think, when the engine can eat and breath like it needs to. Fuel is power and cooling. I like to get all I can of each.
Type at you later,
Dan McEntee