Don't use a sabretooth for that application.

Why do you want it to run both ways? There isn't much point in being able to do that and if you switch the direction in the arena when its spinning one way suddenly you'll throw a huge amount of current through the speedo and probably kill even a victor.

With spinners you want things to be as simple as possible. I've tried both variable speed and on/off and always found the variable speed to be rather pointless and nothing more than a distraction when you are trying to drive your machine.