Great job, as a DIY afficienado, I applaud you...I have printout of ebb and flow set-up you copied and I never tried it because of the weakness you mentioned...I have kiced aroud using pvc t's/T up for netpot sites allowing drainage/roots into large pvc tube.

I found a drain field pipe at hopot for under 10 dollars and the t"s ther efor under 5...
I would build one, but I am in the middle of perfecting my aero/drip/dwc setup...keep it up, I look forward to what you come up with next...lw