another mounting option that might help you:
http://www.torklift.com/index.php/products/auxiliary-battery-storage/hiddenpower?w_page=hiddenPowerDJ, im assuming you have a 12v compressor fridge if you're drawing 3.75 Ah.
I know you travel in remote places .
As Skip stated , I had the same dilemma . Running 2 6v's and carrying a 12v. as an emergency batt. in case one the 6 v's goes bad, which I have had happen.
If you choose the 6 v. route , even if you don't hook it up , I would carry some kind of charged 12v. power source just in case.
Being that I was carrying 3 batteries (two 6's and a 12v.) I now run 3 , 12v's at 105 Ah each . Total 315 amps.
I use (3) DEKA AGM Deep cycle RV Intimidators. grp 31 . (if interested - specs on it) .
http://www.remybattery.com/Intimidator-8A31DTM-Group-Size-31-AGM-Marine-Battery-P2361.aspx