Need advice on a 75 gallon durso/sump setup.

Hi everyone, I'm new to the forum.

I recently got a good deal on a used 75 gallon (48x18x20) setup, that came with a 30 gallon sump/fuge. I have a few questions regarding how I should setup a durso standpipe and sump.

The tank came with 1 hole drilled for a 1.5" bulkhead at the bottom right of the tank w/o an overflow box put in. It looks like they were just using a 1.5 pvc w/ a 4" increaser at the top for some kind of ghetto rig overflow w/o a box.

From reading on how to do a durso, it appears that the 1.5 may be overkill for this setup, although there is only one drain on one side. I also know that for a durso to work correctly, the 1.25 needs to go into a 1" bulkhead. Im not sure if should stick with the 1.5, or try to figure out a way to reduce it to 1.25 and creating an overflow box around it. Also, is there anyway to reduce the 1.5" bulkhead to a 1"?

I'm still pretty new to this so any input would be helpful, thanks.

 

Are you able to drill it? It would be better to have 2 holes, one for drain/one for return.

 

I intend to drill one for the return, it did come with a HOB return line.

Im not so much concerned with that as getting a proper overflow going.