Balance -shmallance! I have to separate all my AGMs and do them one at a time at home to ensure they each get to 0.5amps/100AH to be truly full before I put them all on the same Float at home on stick-house shore power.
I have no clue what you have to do with Lis in a bank, but if it is anything like AGMs you can wire them up for the camping part anyway you like.
It doesn't matter what you do when away camping off- grid doing 50
-90s as to how much each battery is delivering /losing. Just get there, do it, and get home. Once home, do it all up right, per Mex's rules and wait for the next get-away.
I suspect the OP can use any wire he wants for the fifth batt as long as he ensures each of the five batts gets done up right as often as its specs call for. (Same with Wets or AGMs)