The wire in the middle is to make the pack a saddle pack for those of us who run cars that need them - it makes no difference. I run saddle packs in my tc3, basically because I also run a 10L2 which needs them.
It sounds like you have a cell soldered in backwards. Check and double check to make sure you have soldered each "bone"
positive on cell A to negative on cell B
positive on cell b to negative on cell C
positive. . .yada yada yada
RC10L2.5W - RC12.4 - RCNTC3(bmi) - TC4 (modded) - B44.2 - plus rent-a-rides! :D