Duralite's have the 'safe charge system' and if you charge at higher then 400 mAh you'll blow the circuit, they also have a built in balance charger so balancing isn't necessary.

i was having problems with mine dropping to 7.1 under a 1A load and it turned out the connection from my loader was corroded. try the plug from your charger in the load tester and see if your readings change.

kc