ORIGINAL: FatOrangeKat
All of the manuals I have seen thus far (Thunder Tiger, OS, Magnum, Super Tigre) recommend no more than 20% nitromethane, and most of them say that if you are going to use more you need to make adjustments to the engine (timing?).
The adjustment is usually a couple of head gaskets and a colder plug. Exactly what PiperChuck said.