size holes to drill

So im working on getting my new 54 gallon corner tank up and running but i wanna drill over flow and return in back. Im not shore what size hole i should drill for for the for the over flow i was thinking 3/4 not shore if it to big or small and like half inch for return it will be going into approx 10 gallon wet dry

Here's a link for what size for what returns. It worked for me

Savko Plastic Pipe & Fittings

Here's the flow rate chart
Bulkhead Flow Rate Art

I'd also go with 3/4 for your return - half inch pipe is just so small and flimsy... don't want your pump's flow rate restricted by your pipe size!!

What kind of return pump do you plan to use??

I would always err on the side of larger holes. Large overflows reduce noise and large returns are more efficient. Once biofilm starts growing in the pipe, you can expect the flow to drop off by about 20% or more, so always keep that in mind when calculating flow.

Plus any bends in the pipe will reduce the flow.

I would go with 1" down and 3/4" return. That's what I have on my 75 gal, and it's nice and quiet.