I've seen some calcs which include Euler's buckling load equations (column load), but unit-wise they don't make much sense. I think I will go the usual path of 'make it big enough so that there's no way anything can go wrong' that most people seem to take. Safety factor of 100 will do:)

For the lead screw I'm using standard M10 or M12 threaded rod and I will stick to standard ID 10mm angular contact bearings. It seems like going miniature can cost an arm and a leg.

Regards,
dsc.