Leadscrew end thrust calcs for Max mills?

I'm working on a thrust plate/motor mount for the MaxNC. Going to be
doing some testing on a bearing, and really don't know how to calc the
actual thrust loads.
I'm assuming a worst case of about a 210 oz/in motor and 1200 rpm max
speed (knowing torque at that rpm won't be that high). I plan to make a
test rig and run the bearings in a vertical direction using a motor to
spin the inner race, and hanging a weight from the fixed outer race. I'm
looking for a ballpark number in actual pounds, that would at least
equal a worst case load. If some of the servo setups some folks are
working on using real servo motors and Gecko drives run at a faster rpm,
I'd like to know about that too!
(Will also be doing some testing for succeptability to brinelling to
account for unplanned crashes)

Thanks,

Jon