I don’t think it is that hard. The goal is to match climbs, and climb is determined by thrust. The most direct way to control thrust is by regulating the prop, because that’s where thrust comes from. Not from the engine or battery. I think everyone would agree that for any one prop diameter there is only a certain amount of thrust that can be extracted, regardless of how fast you spin it. If you want an electric model to be equivalent to a gas class, can’t that be done by simply placing a limit on the electric prop diameter? For example, to compete in 1/2A gas, place say a 6″ prop diameter limit on the electric models. No restriction on the electric motor or battery – let the participants optimize those over time. If after some experience the electrics are getting too high or not high enough, just adjust the number. Simple. You can measure it with a ruler. Otherwise except for that one difference – i.e. prop diameter for the electric instead of engine displacement – the event rules are unchanged.