Flood tray depth

curious on what is the optimal flood tray depth. I see that most trays you can buy online is 7" deep. I plain on using a regular 1 gallon pot with hydroton and growing plants that will probably be 2'-3' high. They have these perfect size rubbermaid trays at lowes that is only 5 1/2" deep is that adequate enough?

Yeah that will work if your using rockwool cubes, but if your using hydroton you might want to go with a drip system.