From my experience, the yellow print result with Epson Ultrachrome K3 ink appears to be a bit more variable than the other inks for some folks particular x900 series printers (dE and dH shifts greater than the other colours, despite regular tight calibration). We have one customer that has two 9900 proofers, one machine behaves - the other does not and it can swing wildly in and out of passing F39 for the solid Y patch simulation (which is of course not using pure or solid Epson Y).
Stephen Marsh
