Chemically speaking nitromethane is so stable, its flashpoint and heat of vaporization is so high that nitromethane is almost like water. According to the literature on the subject, you only get an increase of a couple of hundred rpms for each additional 5% of nitromethane in your fuel mix. As I have said before, two stroke engines are so well scavanged by the exhaust that they need more oil in the mix to provide enough lube, and also help with keeping the engine cooler. Correctly directed air flow is essential to cooling your engine properly. Remember you want to channel your air in one specific direction, so don't start cutting holes in your cowling nilly willy, you will create unwanted air eddies thus getting a non-functional cooling system. the small hles and or slits on the front of the cowl act as an air dam directing the air flow into the engine compartment. The exit hole should be 3 times greater in area size. Scoops or fairings on the intake or exhaust sides of your cowl can also help improve air flow cooling. Oil does some secondary cooling thru lubrication to reduce friction, high heat denatures most synthetics used in american fuels, this is the reason a small amount of natural castor oil is used fuels to avoid complete loss of lube at high temps. Whats this have to do with predetonation, you may ask? You are running a Diesel two stroke, with no way of changing timing without changing the engine mechanically, or thru chemistry and sometimes both are needed to solve the problem. Try restricting your muffler to slow the scavanging and getting more fuel to stay in your engine, then lower the compression will help even more, then find the proper prop and glow plug for your engine. Then fly the heck out of it!!!!!!!