You'd have to get your hands on Roland's tech sheets ....
I'm no electronician, (studied Jazz , sorry ) but Piezo being "uber" high impedance they absolutly need a "buffer" of some sort to be carried through a wire longer than 6 inches...... that's where the haxaphonic kit would come in.
I completed a GK project bass , check there ;
http://www.unofficialwarmoth.com/index.php?topic=6342.0
Pitch to MIDI for bass guitar doesn't work.
I tried Axon , Roland , the latency is un-playable.
It's OK if you do "spaced out" chords and Pads but doin' a tight groove with a drummer , forget it !
Try the V-Bass from Roland , almost no latency , not a lot of synth sound choice but at least , playable.