The best advice I can give is contact GV
GEAR VENDORS, INC. 1717 North Magnolia Avenue, El Cajon, CA 92020
Toll Free 800-999-9555 "¢ Telephone (619) 562-0060 "¢ Fax (619) 562-1186
They should be able to answer all your questions.
All I've heard is that when compression braking going down a grade you lock out the GV unit so it's not engaged. However, I don't know if that's correct or incorrect, best to check with the GV folks.
Good luck with your new coach and have many fun, safe and trouble free journeys,