Originally Posted by maddmaxx
About the cassette not coming out far enough or coming out to far. If you are using the CS7800 cassette, there is an instruction on the Shimano site that requires the installation/use of the "low spacer" when installing on a 9 speed hub. The spacer appears to be 1mm thick and the instruction is SI-1Z80A. If this spacer comes in the cassette originally it will have to be removed for a 10 speed hub. Don't know if this helps but it opens a new line of investigation. If not the derailleur then possibly the cassette.
That's not it, since I've had this wheel/cassette combo on other bikes and worked fine. Also, it works fine on this bike with the Ultegra cassette. I think something's wrong with the derailleur. Perhaps I'll try installing it once more just to see if there could have been anything wrong with the initial install.