ok makes sense. I am like you, for my local track we tend to use something like 18-26 amps or some use 16 to 24 average watts to pick the better motor.
I felt the 20 amp RPM was a good all around rpm number to gear from. Just recently my buddy has found that for 19T motors the robi seems to really hit the nail on the head when it comes to their gearing calculator.
For stockers I think it gives too much range. well I should rephrase that, if you use the same type of motor it is useful, but say your benchmark is an Epic roar stock and you are trying to use the robi to gear a Monster its all over the board. Like it once told me to gear a Monster lower and I know you always need to gear a Monster higher maybe only a tooth in some cases but it always needs more gear no matter what the track.