High speed turns in reverse only (skid steer)


I have a skidsteer rover and I’m just beginning to tune it.
When I drive it forward with the radio it works pretty well, forward left right, etc…
When I push back on the throttle and give a slight steering angle, the rover flings around at high speed with an angle that in no way resembles the steering command.

Are there any parameters that only effect reverse steering?
Or is there something else I am overlooking?