Boy Hatch, you sure do seem to get the most out of every inch of space. I just got back from picking up parts for an aeroponics set up like yours. I was not able to get the screw in pvc plugs so I got the glue in ones. I am worried about them getting clogged and not being able to take them apart for cleaning. Have you had to unscrew the risers to clean them and the misters.
This is probably the wrong thread for these questions, I have been jumping back and forth from this thread to the aero thread, sorry. If this is a problem let me know cuz I am coming up with more questions about this by the minute.