Return the stick to it's factory vcore to ease power draw at high frequency.  



Test them one at a time to see if you can push past 55GHs.

Start at 300MHz, unless you get 68GHs (0.228 x 300) don't go higher .

Try with and without the hub - single stick.  

I find my dell's usb port does pretty well with a single stick, fan, no powered hub.

Once you get 68GHs, bump the freq up by no more than 25-50MHz at a time, test for 24hrs...

One at a time first and you should be able to find where the bottleneck is.