Overflow Box Flow Rates

I have 2 ESHOPPS Model PF 1800 that are rated for 1600 gph each. I figure I am only getting about half of that each. Is there a way to get more gph out of these overflow boxes?
I know I will never hit 1600 gph each but I would like to get more out of them if possible.

I am getting enough water to the pump I just want to increase flow through the OFB to at least get 75% of what it is rated for so I can get a new larger pump.

Been doing some research, I have 4 Ball valves and 3x 30 degree elbows on each of the 4x 1.5 " drain lines. Will this drastically reduce flow to the sump? Should I remove the Ball valves?

Thanks Strollo,

I just used rigid plumbing for a cleaner look. And in all honesty when figuring flow loss I only considered the return. I didn't consider the drain side of setup.

I am assuming I can find 1.5" soft hosing pretty readily? Should I look for a specific type of hosing?

I have two long runs from the left side of setup and two short drops on the right, so cut off the fittings and just clamp the hosing to the straight drops from each OFB into the sump eliminating all of the fittings and ball valves thus increasing gph.

Here is a pic:

yep, each box has 2x 1.5" bulkheads.
I am using a 1.5" U tube on each box now instead of the standard 1". When I put dual U tubes it causes the water levels to drop in the skimmer side therefore causing air to settle in the tubes.

So then by removing the teeth (all of them?) it will increase the flow back into the skimmer raising the water level. Eliminating the need for removing the ball valves? I
Can dual 1.5" bulk heads handle the dual 1.5" dual U tubes? I imagine I need to use the same diameter U tubes.

What about the 2.5" pipe lifts on the drain side? Whole reason I installed them was because the skimmer side couldn't keep up with the 1.5" U tubes. Thinking aloud here. if I just removed them (lifts) and cut the teeth if that would increase the flow without dual U tubes?

Will be elated if I can get 4K. I will be happy to just get what they are rated for.