Pre-load as in two ball circuits sprung together? If so it eliminates all backlash so long as you don't exceed the preload. You may still get a wobble if the nut isn't perfectly aligned to the screw and accuracy is limited to tolerance/stretch of the screw, but no back-lash.
To eliminate play on the shaft, maybe fit an angular contact race at one end and a spring at other so you pre-load that to.
Then all you have to worry about is flex in the connection between bed and tool tip. Hope you have plenty of iron in there