I was going to fill just the net pot lid. I've seen some builds around online that used a dripper ring on top of a net pot full of hydroton that drained back into a reservoir. In my case, that reservoir is just the bottom of the bucket. In my case, the second bucket just gives me more reservoir volume without raising the water level, and easier access to
pump it out.
What I'm suggesting would be a sort of Frankenstein of this with a regular DWC bucket underneath, which I would imagine could allow me to run the DWC level a little lower without worrying about the roots drying out.