So this is my small version of the overflow.
Nothing fancy but since its right up near the top trim of the tank, you barely notice it. So much nicer IMO than having a huger overflow box. I wouldn't do this in a bigger tank or with a large return pump though. This along with a gate valve regulated drain would be ideal. I didn't have a second hole drilled though for an emergency drain so I couldn't go with the gate valve safely.
Hopefully it will work out like this though!