Are folks using a LH ballscrew for the Y axis on the mini mill or RH and relying on software to compensate for the normal LH configuration? Also, how are the ballnuts mounted?

I haven't done a Mini-mill, rather the mini-lathe, and I used LH thread on my cross slide. Really wasn't neccessary, as I have no provision for manual control, and the computor dosn't care less whch way it is told to turn the motor.

I can't answer your second question sorry.

Need pics of that conversion that is the next one I'm gonna do.