What I think is..

When you increase the Bore of the engine.. the same amount of pressure (expansion) is applied at the same rate per square inch over a bigger area.
Result? More "bang".

I also think that while stroke does change max RPM, its ultimately related to other factors. (Ferrari V12 that has the throttle response of an S2000 4 banger!)

Its important that any change we talk about DOES NOT AFFECT other factors in a LINEAR fashion. Every single calulation has an "optimum" point to achieve what we want.
Balancing all these points is what building a great engine is all about.

Another thing... why does a diesel engine produce more torque than a gas burner? The theory I heard is that diesel explosions are "slower" than the "flag bang" type explosion gas engines produce. So in effect, the power stroke "lasts" a longer time. This also explain why the 1.8 liter VW TDI tops out at a tops of 4k RPM. A far cry from the 8k-9k that gas burners can go up to.
And since nitromethane has a higher calorific value than gas, its "gang" is more intense and shorter than one produced by gasoline. Hence higher RPMS can be achieved (taking displacement into account)

I wish I had the energy to whip out my physics book.. look up the formulas and use the ideal gas law to come up with a mathematical model for this! (ahem.. anyone else up to it? or know software that does this mathematically?)
Billyman.. where did you get that software? Sounds like that thing can keep me busy for days on end!! lol

ram