help with overflow

[Argentiner]

Just setting up a 175 gal bowfront with approx 50gal sump. Have 2 overflows on each back corner with 1" drains that go up to the top of the overflow and two 3/4" returns that I connected with a "circle" manifold with 11 nozzels going back to the tank. I have a Coralife Turbo-Sea 1270 gph circulation pump for the return line. The question is: I had to cut back my pump to less than half in order for the overflows to keep up and the nozzels are barely putting out any flow. Should I cut the overflow drain PVC pipes down to get more head pressure and faster overflow rates? Or would this even make a difference? How can I increase my return flow to the tank? Just new at setting up a sump and maybe I'm missing something here...