Consider putting that extra pair of 6v to use as the 12v supply.
Use a $40 DC/DC 5a converter to draw off at 24 and keep the 12v house supply charged.
Victron 24dc to 12dc converterPossibly the $60 version at 17 amps could eliminate the 12v battery completely. Slides, jacks, brakes may need the battery for higher loads so that may not completely work either.
A 5a battery charger (I recommend Battery Tender brand or marine charger that provides a continuous float) powered by the inverter would also be an option to keep the 12v battery topped off. Probably not as efficient as the DC/DC converter but total power may not be an issue.