Come on guys - the OP has a clue and is looking for constructive input
Not sure where that rule of thumb came from regarding X watts of PV array with Y amp/hrs of batteries - it might work for some folks and for sure does NOT come close for others - I have 560 watts of PV array and just two Cosco GC 6's in series with NO plans for any additional batteries - been working great for 4 or 5 years now.
Understanding how the rig is being used and what is expected from the PV system is what's needed - I believe the OP knows what he is looking for
Two batteries 6's in series or 12's in parallel will do the job just fine. Some rigs including mine have ZERO room for additional batteries and further more we do not need or want them