I just replaced the 2 group 24 AGM batteries with 2 Litime 100AH smart batteries. I did remove the OEM battery box and vent, replaced it with 3/4" plywood (18"x24") and boxed the batteries in with 2x4s (17"x11"), painted the box, top & bottom with automotive undercoating. Used silicone form-a-gasket to seal the original opening, screwed it down and then undercoated the entire area from the bottom, Used 24" bungie straps for the hold downs. I removed the vent hose & panel and used the cap from a can of spray paint to close off the vent opening, it fit perfectly. I cut 1/4"to off the top of thecap, inserted it into the vent put them together and remounted it. I'll post photos tomorrow.