Optimal ballscrew diameter for lathe

[vre]

For type C end support and 3210 ballscrew (27.3mm root diameter / 1900mm length / mass 10.64kg)
Critical angle speed 1344 rpm
Max column load 29764 newton (if we make the assumption that force can be represented in kg is 29764/9.8 = 3037kg )

For type C end support and 4010 ballscrew (34.1mm root diameter / 1900mm length / mass 17.1kg)
Critical angle speed 1679 rpm
Max column load 72453 newton (72453/9.8 = 7393kg )

For type D end support and 3210 ballscrew (27.3mm root diameter / 1900mm length / mass 10.64kg)
Critical angle speed 2039 rpm
Max column load 59528 newton (59528/9.8 = 6074kg )

For type D end support and 4010 ballscrew (34.1mm root diameter / 1900mm length / mass 17.1kg)
Critical angle speed 2547 rpm
Max column load 144906 newton (144906/9.8 = 14786kg )

These are ideal calculations without safety factor in reality because the carriage of lathe has on the ballnut (shortens equivalent length) and the ballscrew is mounted in the side of lathe (side load is worse that centered load) maybe these calcs are wrong in good or the bad way.

In reality from calcs seems that 3210 fulfill the 1000rpm in all setups with a good safety factor
but i have doubt for max column load what is your opinion for side load is enough in case of 3210 ballscrew ?
Where is better to mount Z axis servo near the spindle or near the tailstock ?
Also where is better to mount X axis servo in the side of hand wheels or the opposite ?