I am not sure how you would accomplish not breaking siphon in an overflow tube return. Maybe someone who has this set-up and has licked this issue can respond
One design that I know that elimiates the problem is the use of an overflow box. This is usually installed in-tank (usually in the corner or mid point on the back) and it is plumbed from the bottom of the box to the sump. It is a sealed box and has openings for tank water to drain into that is returned to the sump. There is no siphon to worry about. If you pump shuts off, the tank will drain to the sump to bottom level of the holes in the overflow box then stop. When you re-start the pump, the tank level rises and water overflow commences. Simple and foolproof. As a matter of fact I take advantage of this in feeding my reef tank. I use the Red Sea wavemaker which has a reef feed mode that shuts off the MP and all but one
PH. This allows food to reach the corals at the bottoom of the tank and prevents a lot of food from being sucked into the overflow - waste and
NO3! Works really well. I think that there are some retrofit overflow box setups but it will require you drilling your tank.
HTH