I changed my original single 12v that came with the 5'er to 6 volt yesterday. I have a use for a single 12v battery in another application so this was a good time to make the switch. I used 2 Trojan T-105's. The only modification I had to make to the battery box was to trim the front of the battery tray for each (plastic) to allow the slightly taller golf cart batteries to fit. No other modifications were required and they fit like a glove. I will see if I can upload a picture. I still need to mark the cable that goes from the positive from one battery to the negative on the other, but don't have the tags yet. It was a tight fit, but probably seemed worse that is really was because these batteries weigh a bit over 70 pounds each and are hard to handle in a tight spot. They don't have a built in handle wither so I made one with several loops of heavy twine. I looks strange, but it worked great. Thanks to Jayco for providing cables that are "just long enough".
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof