Think I finally cracked it.
Using QuadR800 driver & my non-supported office printer (Epson TX810FW) and using my existing BLACK tiff image, I first tried the magenta cartridge with all others not used, but that didn't work.
Tried selecting the yellow cartridge only and that worked. Started with ink density at 100% but the lowest resolution, and increasing the resolution each time. Went from a light solid yellow print to a much much darker yellow print with the ink "blotting" on the paper.
Time to put my supported R210 printers back online and test them.
Thanks again everyone.
Keith.