Round trip is less than 10'... I kinda figured that the GND would end up being too small, but the battery ends of the B+ I crimped as-per your detailed instructions on your Compass Marine page. I bought an FTZ lug crimper when I rebuilt the DC system on our trawler about 4 years ago. I treasure the tool... I use it all the time for friends too.
One thing I noticed it that the charger lugs I used (power, not flared starter) were filled with anti-oxide stuff. The grey paste you use in wire nuts if your house has aluminum wiring and you connect aluminum to copper. I didn't think anything of it at the time because I assume it wouldn't add resistance, but could that be causing excess resistance?
The other ends (at the charger) are pretty stout factory connections. I will reexamine them next weekend because I guess I need to get back up in there to replace the GND wire anyway (it is a pretty big effort requiring me to remove some exhaust tubing to get to... and even then, it's awkward). So I guess while I am in there, I will reexamine the path of trying to beef up the B+ wires too. **sigh** I had hoped not to have to do that <see below>
My original question also still stands. Let's say I increase the gauge of just the GND. Would charging performance become "unbalanced" if I place the existing B+ leads in several (or just 2) places across the bank? Specifically because, with an 8-cell bank, I have had to put batteries in separate boxes about 3' apart connected together with 2/0 wire.
Thanks!