I am starting to lean towards the following upgrade:
1) Upgrade converter to PD 4655 MBA ($193.00). This will enable bulk mode charging (14.4v).
2) Add another vented battery box and tee into existing exhaust (top vent). I found a box on ebay that has a lower side vent that should enable connection directly to the existing box. This will enable use of that lower vent preventing drilling another hole in the trailer floor.
Battery Box with Side and Top Vent3) Purchase 2 Duracell GC2 6V batteries from Sams ($93.88).
Always welcome critique and opinions.