As noted, parallel charging can hide some changes in the individual packs. You can get a good idea of the pack at the end of a flight. Look at the cells by putting a single battery on the charger or use a cell checker, many inexpensive available. You can also look at cell voltage under discharge load to the pack and see if they are different and compare packs, see the battery discharger thread. Finally, it is best to charge individual packs and balance, at least occasionally. PowerLab and iChargers will also check internal resistance.
The Squids that I've seen advertised are cell count specific, at least for the balance connector, not power input. So you can have separate balance connectors for 4, 5, and 6 cells if you use different packs, or use the parallel board. The safest board is the MPA fused board.
http://www.progressiverc.com/fma-multi-port-safe-parallel-adapter-for-jst-xh-t-plug.htmlI use that with the PL8 charger. You can see the shielded power cord ends made to fit the PowerLab chargers. The shielding has to be removed, or worked around with adapters, to fit other chargers. The shielding prevents shorting if a battery is on the board and you unplug from the charger - not a normal procedure, but could happen.
The Zippy Compacts, 6S 2700 25C discharge also say up to 5C charge. Best for the batteries in most cases is 1C, for all brands. That's my routine charge when at home and planned ahead. I may use 2C at the field, and if a power source is available, not just my car, higher is ok. If you want faster, look at the slow portion of charging, the finish at C/X where you can choose the x to be 5, 10, or 20 as usual numbers. That is a slow top off for few mah. C/5 will speed the process and work well unless you are using every last mah to finish a flilght and stay at 80%.
A reason to use 24V input instead of 12 is that the charger then doesn't have to step the voltage internally and use some of its power. That also means a cooler charger.
Quad versus parallel - Unless you compare specifics, in general, the quads are not the quality of the iChargers and PowerLabs.
Fred's yellow box is cool.
Thanks Howard