I made a two cell and a three cell harness similar to the one above (mine do not have a seven wire connector at the charger end).
They work well if you have a good way to connect the wires to the cells. The wires can be soldered to magnets, but that can be a little tricky 'cause if you overheat the magnet it will lose its magnetism. Instead, I just soldered ring connectors to the wires and used an unsoldered magnet on both sides of the ring connecter between two cells. I started with ready-made two-cell and three-cell harness extensions available at HobbyKing and just cut off the non-charger plug.
In a two cell configuration there would be no blue wire and the red wire would connected to the yellow wire at the cell. It may be obvious, but in a three cell (four connections) configuation care must be taken to connect the green and the yellow wires in the right order. Your charger will proably complain if you don't! A properly wired cradle would avoid this concern.
Note that inexpensive B6 clones often do not have very good balancing tolerance. For that reason it would be a good idea to use a DMM to verify how well your charger is balancing your cells. My X-charger B6 clone had lousy balancing tolerance and often considered a 150mV difference to be balanced. I upgraded to an iCharger 208B to solve that problem. If you want to do balance charging and don't yet have a charger, I recommend that you verify the balancing tolerance of the charger before you buy one.
This post has some good photos of examples.