UD ... I have not tried it BUT the manual states there is a "In Note Range-High" and a "In Note Range-Low" for the Voice Processor.
In the Global: Midi (Tab) Midi In Control.
Low (for left hand triggering) would be 0.
I would assume setting this where the KB split is and the upper at 76 would do the trick. I will give it a try and let you know.

Kbrkr ... If you want to travel to Long Island the beer is on me!!!!

This KB SMOKES!!!!