Dimension Engineering makes a LVC called CellShield that monitors the individual cells in packs. You could use the series adapter I drew up to hook the balance connectors from the two 3s packs together so that all 6 cells in series could be monitored by the LVC. They might be working on a car version for it, but I haven't gotten a definitive answer from them (I've offered to beta test the car version if they were to make it). Check here:
http://www.rcgroups.com/forums/showthread.php?t=566012 (I'm TMetalMan)
http://www.dimensionengineering.com/CellShield.htm
SH Z-Car, Custom Crawler, 8s Savage,
12s XTM XLB 1/7 buggy,
4wd 4-link rear/IFS Pro4 truck,
Custom Hyper 10 Short Course,
Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz