I'd recommend some different batteries. For the price of those 11.1's you can get something much higher quality. A few bucks more will get you 2 of these...
http://www.rc-monster.com/proddetail...eu3s5000car25c
Also check out polyquest, or flightpower.
There are threads in the general electric forum about making a balance harness for charging both packs at once. Yes, it is possible ;).
J.