I'm another Magnum 2812 user. Installed it over a year ago. With a single house bank of 220 usable amps, it worked fine for the great loop. For overnights without using the genny, there was plenty of power to run two fridges, minimal LED lighting. Micro a sandwich or lite duty dinner, Make coffee in the morning and heat up a cold cup in the micro, pull the anchor and start up the engine.
(however, for dinner, we often made dinner while still running to save power for later, using a crock pot or microwave.)
PS we could not run the stove, AC or grill off the inverter as they are 220v.
Overall, very happy with that simple set up. The eng and gen start batteries are separate, but can start the eng with the house if needed (switch).
And, absolutely, get a battery monitor, and set your inverter to shut down if voltages goes below 12.2v.