More Questions on Z-Axis Drive

Sorry to repeat but I guess I asked my questions using Jakes subject line.
(duh!)

I'll probably have a similar issue to the one Jake has with his Z-Axis.
(and yes Jake, My mill also has a clunking noise going down below a
certain point)

The question I have for the group is: How big a Servo/Stepper motor do you
recommend for the Knee? oz/inch ? Anyone? Mine is sort of tough to
turn. (about 15 pounds roughly) Well oiled but I think just heavy, damned
heavy in fact... Could I go 4:1 or 6:1 on the pully?
If I build the larger pully to do it will it have problems with the
stepping software. (ie: Maximum Steps for a distance) Is there a limit in
EMC settings, say for a maximum pully size??

Any experience on this would be appreciated.

Vince