Actually he's probably not advancing the ignition or running hot. You have to remember that the mix adjustment has a big influence on ignition timing as well. If he's at a peak setting, he's gone rich enough to retard the ignition back to the point where he is still making max power for his setup. The problem is that with that setup that max mix setting is too rich to produce the best burn, so he's losing power. Going to a colder plug and less nitro or less compression will retard the ignition, letting him run a leaner needle setting, thus getting his mix closer to optimal for power while still having the ignition timing right.