Can you make an accurate sketch of what it looked like, and how you are planning on changing it over?
I suspect that you should be turning to a shoulder on the ballscrew, maybe 3/8" to 1/2" diameter. That shoulder should serve as the abutment for the support bearings, and you really only need one locknut to tighten the bearing's inner race to this shoulder.
Generally, a nut with a jamnut is a poor way to preload a set of bearings, even on a simple machine, it is difficult to remove the backlash and assure that the faces of the nuts are not creating a bend in the shaft and a lack of a true running surface to push against the bearings with.
Better to use a single nut, and some appropriate custom machined spacers or shims to create the proper preload to eliminate backlash.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)