I never use a mixed grip (under/over) anymore. I used to (a long time ago), but after sustaining a bicep injury and another time sustaining a lat injury I switched to the hook grip and I've been good ever since. You'll want to slowly incorporate the hook grip into the routine b/c it's quite painful. If you use it on all your pulling movements like RDL, SLDL, Rows, etc you'll find the transition smoother.