Im going with Trojan's plan. The other thread posted this link:
SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank
While it doesn't show how to connect 4 6V bats to make a 12V bank it does go over a very important consideration when you are putting your cables
As I understand it, when doing 4 6V's the two parallel cables
should be the same length and the two serial
cables should be the same length. As long as you can make this happen it seems that the banks will be pretty balanced and there is no need for the cross connects.
It was fun figuring out how to optimize this given my battery
layout but I think I've got it sorted.
Thanks for helping me through this.