Just as a general comment to add: The actual effect on torque is more than just the duration of the burn; even if you extend the burn time of the same amount of fuel energy, then the combustion pressure will be lower (since the fuel is burning more slowly) and the net effect over a longer duration can go either way.
I am not sure I am understanding this:
So are you saying that you think that the effective, or net, torque output will be higher, since the pressure will act more effective even though it is a shorter time?
I have been assuming you are looking at a short rod to get higher piston velocity at lower RPM's for better cylinder fill there, and giving up the higher RPM end a bit, to better match the head. Yes? No?