Ah right, that's awesome! that could be one way around it, I was also thinking of lower containers, wide and low, and and splitting the flooding and draining into 2 of them so roughly half in each one, that would make me less worried about it breaking. Or water storage containers for a van or a flat water butt, they'd be less likely to crack but they're a bit expensive.
That top feed idea is a great one thank you, and I is the growth and yield the same as flood and drain? I have gone with the hydroton and figured I'd sort it out as I go. I actually came to ask how often to top feed during the plants rooting into the pots. The rooting plugs are still wet after a few hours but the stones are just damp. Will the roots grow into the stones this way?