[jacksonpt]

Yep - you can certainly do/use what you have.

IMO - drill the holes at the same height. The line with the strainer guard on it, rotate so it bends down into the tank (the hole will be higher, remember). Put a gate valve on that drain line, and adjust it to run at full siphon handling 99.9% of your flow. The other hole/line, leave basically as you have it pictured (though a strainer/guard is probably a good idea). This will be your trickle/emergency line.

The end result will still be a herbie system, which is pretty tried and true.

The only issue with this will be that when your return pump is off, your tank will drain down to the strainer guard as the siphon will continue to run until it can't pull any more water. This is one of the pros of overflow boxes.