Sabertooth 2 x 32 Remote Control - Speed Control

Hi,
I am using a Sabertooth 2x32A Motor Driver Board. I have set the Dip Switches for RC control (I think I followed the guide correctly).
At the moment we don’t seem to get much speed, this may be down to the motors / batteries but would switching between Expotential and Linear (DIP Switch 5) make a difference.
I assume we cannot use the throttle?