I have 2 1" drains on my tank. However, I'm only using one, but at a full siphon. The other is just an emergency drain.
If you have one 1 1/2" bulkhead, I would think that would be okay. I'm not too familiar with hang on overflows though. If you are worried about it, I would give Tom a call and see what he can think of. They use them on their grow out tanks, so I'm sure he has some ideas.