pigg: The only 5x3 prop I know of is for Cox .049's so that is why I thought you were kidding. But even though a regular size prop might not allow the engine to achieve full rpm, it still would be indicative of the potential and also would show any differences between the three engines, imho. Also, most cars/trucks/buggies/truggies are not at WOT all the time. Mid-range power is usually more important if you are driving on a circuit.

ExtremeNitro: Do not run a nitro engine indoors. You can asphyxiate yourself.