Be careful closing a register substantially or completely, especially one that "really blows". If you reduce air flow in the system you can overheat your furnace. I'm sure furnaces have over temp sensors that would shut them off, but I really don't want to depend on that sensor.
I think talking to Jayco would be a good idea.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof