Hi Starkeeper,
this is the setup I use when playing in split full fingered mode.
Clavinova for lead melody, fonts for styles.
First I turn Clavinova to Local Off ie I don't hear any sounds when I press keys.

OMB Settings
Chord Fingering " Full Fingered "
Midi In: USB ( not sure what your setting would be as you possibly use a serial interface to connect keyboard to computer?? so maybea CBX driver or something.)

Midi out
Midi Channels 1 to 4 : mine set to USB
( you'd have to set yours to whatever your set up is)
Default melody channels in OMB are 1 to 4.

Midi Channels 5 to 16 mine is set to Midi Yoke
( you'd use your sblive card setting.)

Next on the main Voices page OMB :
Voices 1 to 4 , make sure that you enable
the ones you want to use. You can have up to 4 voices at one time. If you just want right hand melody, make sure the others are set to off.

Hopefully this may work for you.

best wishes
Rikki