Well, massive clutch #5 was a bust. I have TWO fry from it.
Two potential errors: 1. I pulled these really early due to the predation of eggs in #4.
2. This was a LONG PVC pipe, and it wouldn't fit into my egg chamber vertically next to the flow, so it was in diagonally (so the eggs touched each other) directly IN the flow, which could have contributed to a problem I noticed, near-but-not-yet fry coming detached.
Anyway, #6 is in the pipes. A much shorter pipe this time, so we'll see if that helps.