I'm no parallel battery expert but common sense would tell me that there isn't that much difference. All the little electrons are lined up and ready to march through the connecting cables. Some of them might have a bit more push because battery voltages might be different but they're all gonna' march. One way to have a more orderly wiring scheme is to use a copper bus. You can install the one lead off the batteries to the bus and connect the devices to the bus. I find it's easier because if you have to mess around with batteries, you don't need to disconnect multiple terminations.
I made these simple ones with a 1/8" copper bar and a 4" double gang box:
The bus bar is glued and screwed into pieces of HDPE, glued and screwed into the box walls. Holes are all 1/4-20.
