Overflows and drainage

I've asked time and time again, and searched and searched, and no one has enlightened me to what I feel is the most important part, and also the last part, of my journey into hydro. I'm trying to find a rough idea of how high to put my overflow in my flood table, but also, how do I drain the table in its off times so I don't overload the rockwool cubes in their hydroton. My seeds are germ'd, my cubes have been soaked, my lights are up, I just want to know how to successfully and safely drain so I can put everything together and start growing again full steam ahead.

Put the rookwool on top of the hydroton 1/4-1/2inch ABOVE the flood line. Actual flood height depeneds on 1. how deep your flood tray is 2. how tall your pots are. You don't want to flood to 8inches if your pots are only 6inches. You know what I mean? I don't use rookwool but in the first pic you can see where I flood to. the next two shows how to place your rookwool on top of your hydroton.

I wasn't going to use pots, even though I wanted to, in previous threads a few months back, I was steered away from it in a flood system. I may just go get them to keep the roots seperate until sexing can occur