Suggestions on battery/solar upgrade due to space issues

Just a couple thoughts:
- Make sure they are legitimate 12V deep cycle batteries. Most of the ones you find at big box stores are not really deep cycle. The real ones are expensive.
- For house loads, putting a secondary battery bank 20ft away isn't a big issue. Look up a voltage drop table with an estimate of peak amp draws but house loads are generally relatively small, so you don't need monster cables.