Let The Fun Begain, New build on the Table.

[Ross77]

Flip the 'Y' axis (top to bottom) arrangement over and add another plate to the back to mount the ballnut and you will always have a nice clean screw

where's the fun in clean? yes you can do that but moves the ball screw away from the Z carriage and reduces rigidity and can lead to racking or binding of the bearings the extra distance can mean the alignment would be a mare as well.

Edit. thought id seen that mentioned before! just realised it was this thread, so same as Jonathan's answer