you should go with single 7' Ls with HHE, if your gunners can't handle the accuracy you should go with single 7' Ns or D's with HHE...
dual 6's (any of those) are also very fun, but they kinda weight too much to use e'm once your crew starts getting fat. BTW use HHE since you need to punch hard DD/CL/CA in blitz or make the "OMFG 500 damage per shell against SS" in GB