I have used the LTV for BiPAP on several occassions, both with adult and pediatric patients, and in acute care, LTAC and home settings.
I do not recommend that you use the NPPV setting though because it is not really a mode - all it does is disables certain alarms, which I think you would want enabled.
I set my pressure control and pressure support settings to the prescribed IPAP level, and my PEEP to the prescribed EPAP level. Then I adjust my Rise time and flow termination to meet that particular patient's needs at that particular time. It seems to work well for me. Good luck!