I've done a few things thus far, nothing too big except my battery bank though.
Built a shelf for the front bin, effectively doubling my storage area up front.
Moved my pigtail box up inside the pinbox, it actually hung down, moved the emergency breakaway leads through one of the bolt holes in the side of the pinbox also, they actually got pinched in two at some point.
Replaced the junky expensive Forest River house water filter with a GE Watersmart filter setup.
Added a light to the front bin since for some reason it was left dark.
Added three batteries and a multi position switch so now I have a four battery, split parallel setup. I'll be testing that this September.
Two on the left, two on the right. Interstate group 27 96ah giving me 384ah of deep cycle goodness! In a few years I'll pony up for Trojan 105, then I'll be unstoppable!
How I tied the vents together. Paired on each side then the sides are paired to the original vent hose. All I had to do was drill holes in the floor for the box vents. It's a 1.25" pvc tee from Lowes, a screw through the hose and tee to hold the hose in place, a zip tie to seal the hose against the tee. I ran it across the top and tied it and the positive cable to the hydraulic hoses.
My switch, it's out of an old ambulance. I have the right batteries on position one, left on position two, and it has a both position.
The wiring, I've since adjusted it some. I moved the positive from the left battery to the right battery leaving the ground on the left battery. Now, the pair acts like a battery bank, sharing the load equally.
Since I can switch between battery pairs my converter will only see two discharged batteries at a time and won't have an issue, and since they'll be separated I can place a charger on the isolated pair.