I wasn't thinking straight in my post above talking about a boost switch.
There's no need to tape a momentary boost switch ON when going down the road. The house batteries are direct connected (no diodes - but maybe a fuse) in parallel with the chassis battery via a heavy current continuous duty solenoid whenever the ignition is turned ON. Running the generator when going down the road will keep all batteries charged up - even with a failed alternator.
FWIW, the heavy duty solenoid connecting these batteries together is one I put in to replace the stock one. The one I installed has silver alloy contacts to keep this system more reliable by preventing the solenoid's contacts from being damaged from corrosion or electrical sparking/arching.
