I'm not sure what Shiranui is on about but 11-11-11-28 got me all the way to 2564(unstable but it was a benching run anyway) with nothing but minor voltage adjustments and a slight bump in tRFC to 147(from stock, 128). Currently running 2400 11-11-11-28 1T 147tRFC 1.5v, completely stable.
But to answer your question, yes. Raise the VCCSA a little, to about 1.15v or 1.2v. Also try putting them back on command rate 1T. I actually had a harder time stabilizing them at 2T than 1T.