Have you seen this?:
http://www.rc-monster.com/forum/show...4&postcount=18
That's for two 2s packs in series, but it's the same concept for two 3s packs in series. The connectors would be a bit different, but otherwise it should be the same. Let me know if you would like me to modify that drawing for two 3s packs in series.
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