your reasoning sounds like it makes sense but it is incorrect. part of the reason for the breakin is to preserve the tight piston sleeve taper fit at the very top of the compression stroke (top dead center). the only way for the top of the sleeve and therefore the cylinder as a whole to expand properly from the inside is to run it up to wot without an overly rich setting. idling even with a heat gun is not the same, because it cant duplicate the heat creation scenario as when it comes from the actual combustion chamber internally when run at wot. using a heat gun cant duplicate what the engine does naturally and is designed to do. there are tremendous temps and pressures created in the combustion chamber/cylinder and that is what you want to occur as soon as possible for proper breakin, and a heat gun cant do that. the faster the sleeve expands on its own natural way the better for your breakin. when the sleeve expands under the engine's own natural internal combustion cycle heat generation it means you are preserving that tight and proper piston sleeve fit, whereas running it cold doesn't allow the sleeve to expand so it just wears out more and erodes the piston sleeve fit. stress relieving the engine with the correct 2 - 4 minute runs for about 12 times/runs of heat cycling with cool down times is far wiser than any idling and heat gun use. idling is one of the worst things for an abc/abn/aac non-ringed nitro engine.