hello, we would like to do more boondocking, and i realize the need for a larger battery bank. we tried to use the 80 ahr batt. that is oem in our 2001 jayco (26' fth) but it is woefuly inadequate. i plan to buy a portable gen to keep the batts. charged. what is better 2- 6 volt t105 in series or 3 or 4 12 volt parallel? also would the batts be damaged if i made a box for them and mounted on my rear bumper?