Return plumbing

[robbym89]

Had a question about plumbing my new tank. It has a thick overflow but no return attached. There are holes on top of the tank that I believe is where it was previously plumbed for return lines. What do you think is the best way to plumb the return line? Drill the overflow? Pics attached, you can see one hole on the corner of the tank, couldnt get the whole shot in but theres another hole on the other corner. Then 2 holes near the front end which I dont think ill be using for anything. I have never done plumbing this complicated so any advice will be appreciated.

 

[P-Dub]

Got a glass hole saw? You might want to consider that option so long as the tank is not tempered. There are ways to determine what panels are tempered. Just Google "how to tell if aquarium is tempered". It might just be your best option to make life ultimately easier.