I'm no expert. But if you don't grow 8 foot plants you should be ok with a shallower container. I've got an Ikea right down the street. Will be checking them out thanks.
I did find some nice wire drawers (like for closets) that sit on top of rubbermaids and will do a SOG with them. The drawers were only $3.50. I got some deeper ones at HomeDepot that were $15 each . I'm using them for lettuce right now to keep the birds away. I'm doing swc with a fountain pump. 6 inches is finefor that. Try it and tell us.