Z axis weight

My z axis weight (the moving Z part) with the router COMPLETE weights 18kg.
I am using RM1605 ballscrew and 425Oz 4A stepper motor on 42V. Do you think I will be able to move the head with this configuration without loosing steps? Do you think it is too heavy? Thank you.

See this thread (read it all): http://www.mycncuk.com/forums/steppe...er-driven.html