Guys,
I have been running 4 Turnigy 5000 mAh 30C cells in 10s2P confifuration in my Aeromarine Stingray at races for the last 9 months or so.
Initially I had one pack severely out of balance, but working with it and cycling the packs slowly, not over stressing them per run during the first few runs seems to have been very helpful. Now after three or four races the packs are pretty well balanced and seem to stay that way. the one pack with the weak cell doens need to be checked and balanced occasionally to keep it in good running order.
The service I received from Hobby King in HK was not so good though, with many questions and asking me to reweigh the order and take and send pictures to help them sort out the discrepancies in my order. Took me over 6 weeks to get my order corrected and recieve what I ordered. If your patient and have the time to dicker with them you can get a good deal.