How much torque before it slips? I may have one or two of these lying around in 120mm length! Win
A bolt head sticking out of one of the six holes in the ball screw would stop the slipping, but I think it will grip sufficiently. Think of the punishment that a MTB fork and handlebars takes - the ball screw is the same size as the bike fork. Body weight on the handle would translate into enough force to break a new bolt, so this should work well for our purposes.