[Gdeaver]

I was referring to a second output shaft to drive an encoder for autonomous mode. If only low gear was used for autonomous the 1 to 1 on the output shaft for the encoder would be OK. If high speed was used for autonomous, the interrupts per second could be a little high. If you do design in an encoder shaft there is some planning as to how fast the robot will go, the precision that is desired and the interrupt load that can be placed on the controller. If additional reduction is needed for the encoder shaft, then plastic gears could be used.
As for the high speed gearing, 13 fps is fast. It takes a very good driver to control the bot at that speed and may be unusable in a crowded obstructed playing field. It's main use is a mad dash to the end zone at the end of the game. The high gearing also affects the acceleration and responsiveness at the lower speeds most of the game is run at. They are all design choices. I personally go for about 10-11 max. This years kop gear box I believe was 8.3 fps and was very usable. Of course if the next game was all about mad dashes from one end to the other you would have that covered.