The Bench can be a complex subject. It depends on what your main goal is in the bench.
I would definitely work the hell out of your upperback as well as reardelts. Both muscle groupings can blast your bench as well as help during the transition phase...chest-->midpoint-->lockout. Keep your shoulder blades squeezed and locked in. Keep the bar from moving or shaking around. Squeeze your glutes and rip the bar apart. These tips will all help you get through the mid-stick.
You can also do some rack lockouts from the midpoint. I would not suggest doing too much emphasis on the "lower half." Going from chest to midpoint can really stress your shoulder girdle and all the intrinsic muscles in there.
Develop a big back, strong tri, have great technique, and your bench will zoom.
Hit sets of 5 strong yesterday,