Matt, You can still avoid out the extra splices and fusible link by leaving the alternator feed alone. For most people skills, that may be best. Agreed, a parallel wire through grommet would provide even higher capacity. Also agreed the motorhome with second battery that needs recharging is different case than the typical car.
One device thats available today which may help is the solar powered battery chargers. Connecting one to the coach battery would help keep it charged.
