On mine the ballscrew will hit the column before the saddle does, so there is also a pocket about 1" dia. for the ballscrew and snapring to ride into, as well as what you have milled off Priddyshiddy.
This gives me a bit more Y, cant remember exactly how much off the top of my head, I will try to measure exactly tomorrow.
Haven't heard from Creavice Reamer in a while, hope he is doing well and plugging away with his projects.
JTCUSTOMS
"It is only when they go wrong that machines remind you how powerful they are."
Clive James