Anti-brake essentially switches off the brake circuit and connects the brake contact to the throttle circuit. I'm not familiar with the Carsteen controller, but it sounds like it's another of the common current amplifier type controllers (not PWM). In this case, modifying one can be relatively easy, but will require real estate for another pot to adjust anti-brake, and the pot can either provide additional adjustment from the band #1 throttle or completely independent of it. If the anti-brake pot is fed from band #1, then of course any sensitivity adjustment will also effect the anti-brake setting which will also need to be re-adjusted. This does assure that anti-brake can't apply more throttle than band #1, but a completely independent control can be range limited to something compatible with band #1.