Overflow for 72"x18"x22"

I'm currently looking at a 135. From glass cages And a 125 from Great Lakes aquairum out of Michigan both are 72" long I am going to build a ghost overflow 24"X1.75"x6" I was think 1.5" holes connecting the external overflow and then three 1.5" holes for a bean animal. And btw I was thinking no teeth but put an egg crate in there to keep things out

I want to center the overflow so I was thinking the holes 12" apart each 6" from the center. But what about the return? Can I just have one return in the upper right corner or do I need one on each side of the overflow?

And any first hand experience with a tank that size from glass cages or Great Lakes? I know GC has had some bad reviews but I find good reviews on them as well they are just the cheapest iv found including delivery.

Thanks everybody !!
Any help is appreciated