5/3/1 Advice for Size

What would you suggest to do for the rest of my workout if my goal is size. I’m doing my main lifts (bench, squat, military press, and deadlift)5/3/1 style with a high rep back off set at the end. What set rep range would you suggest I do for all supplemental work? A basic 4x8 approach?

Also how can I apply the mTor slow eccentric to my 5/3/1 lifts?
Thanks

Might ask Jim about that one. I don’t like to play with other coach’s systems