Need Help on Overflow for 85g

So I got my tank last night and want to get it drilled tonight, it already has a 1.5" hole on the back panel about 2/3 the way up which i'm going to use as the return (split it with two locline heads). Based on where the tank will be situated, I would like to do a bean animal overflow on the side of the tank or on the back - if I do it on the side, I can do a coast to coast 24" glass overflow where on the back, I probably wouldnt go the whole distance. Looking for any advice and what size holes I should have drilled? I've seen mainly 1" but can go bigger if needed. Also, will a single 1.5" be ok for the return?

Another option could be to use the 1.5" existing hole for the return but from what I've read, the bean animal is the ultimate when it comes to overflows. Any advice would be greatly appreciated!

 

The return pipe depends on the return pump.

About the overflow it also depends on the return pump, but 1" handles a lot of flow, i have bean animal a 1100GPH rated pump i guess is sending about 700 or less to the tank, and 1" handles the flow from the pump, i have to close the main drain about 1/3 to get the full siphon to work.

 

The return is a mag 1800, its 1100 GPH at 5', so will probably be closer to 1200GPH.

For the bean animal, if you have the main drain dialed in correctly, do you have to restart the siphon or does it do it automatically?