An imbalance between cells can only be corrected if ALL cells are connected.
You want a LiPo battery management system on the battery, one that takes a simple 2 wire power source
That is the main charging current. The balancing currents travel thru smaller gauge wires.
See attached image of a 3-cell LiPo under recharge on a Turnigy charger.
Look at the earlier reference closely:http://www.all-battery.com/protectivepcbsforli-ionandli-polymerbatterypacks.aspx
You will see the multiple connections. For example:http://www.all-battery.com/protectioncircuitmodulepcbfor111vli-ionbatterypack3cellswith65alimit-pcb111v65a.aspx
Charging at 2 points only cannot work because the cells cannot have exactly the same capacity. Inevitable one cell will overcharge. Overcharging not a good idea on LiPo cells. They contain finely divided Lithium metal and can burn vigourously when unhappy.
Trust me, I worked as a chemist with Lithium. You not want to see it catch fire.