raised grate for sog flood systems?

so i was thinkin in sog flood and drain systems like this... https://www.rollitup.org/hydroponics-aeroponics/15030-batch-clones-rockwool.html you think a deeper tray would be good and the clones sit on a grate or something about 3 inches from the bottom, so the roots werent just limited to growing in the rockwool only, they could grow down into a pile underneath everthing, would this work u think? or would the exposed roots get to dry in between the waterings for a flood and drain

Use hydroton under the RW...It is great for space and the roots
love it.