Drilling holes in tank wall for ghost overflow like setup

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Hi all.
I'm am trying to determine the size and quantity of hole/s to drill in the wall of my aquarium.

I'm am doing a glass version of the ghost overflow set up for bean animal.
The drains are 1" so I already limited my turn over to 600gph right?

This leads me to my next question.
What size hole should I drill in the tank?

1 hole at 1.5" would produce 1400gph

So does it make sense to drill just one hole or should I do two? I do realize I'll never see that type of flow because of my first restriction in drain size.

Looking for help/recommendations

Thank you

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Bump, anyone.

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So I ended up drilling two 1.5" holes in the back of the tank. After reading about the bean animal again I now realize that the 1" bulkheads are not going to restrict my overflow that much. It's the pipeline after the overflow. So I'll add a expansion to 1.5" to run 1.5" drains after the balkheads.