You're right, it does largely work with NTSC, though not in interlaced with the Denise adapter. Regressions seem to happen more often with NTSC as well. I'm just feeling a little defensive, so I'm sorry about that. (I also had a less clear a picture of your intent as you edited your posts after I replied to add more detail.) I've gotten numerous "you're holding it wrong" types of comments in other places suggesting, in essence, I should live with it and work around the problem with things like a separate RGB monitor. It's important to me that it be very clearly understood by those coming across this thread that I am trying to use very boring, claimed supported scenarios that should work.
DiscreetFX hosts Open Video Toaster, and I suspect they share my desire for Toaster to be usable with the ZZ9000. As of right now, it's not without a second monitor because of the NTSC interlaced issue when using the Denise adapter.