I wrote the above too soon.
Weird stuff -- downloaded and installed both the new Epson driver and new QTR. Ran a small test print at 720 and it was okay. Tried running a 10x15 print on Innove Smooth Cotton at 2880 unidirectioal. It printed okay until about halfway down when the LLK/piezo flush kicked in again on the highlights. Ran a smaller test print and the entire print had the piezo flush pink in the highlights.
No flush fluid shows up when I print the standard test page from the Epson driver.
Checked the LLK quad curve for the papers I use and it is a string of 0's like you said.
Are there any advanced settings I need to make with the 2400?
Going to abandon ship for the evening and see if my subconscious comes up with anything overnight.