So with the ball screw it needs space for the mounts top and bottom- so doesn't work with the Vee bearing rails :(
I went for SBR16 - supported rail bearings- would have liked square profile but the cost was too much.
This is the state of the Z axis at the moment -getting there :) waiting on the long bearings for the rails- will be going for MDF front plate at the minute and changing to aluminium later I hope :)
The clearance on the X axis bolts is tight but clear is clear :)
Click image for larger version. 

Name:	20180427_170454.jpg 
Views:	841 
Size:	325.2 KB 
ID:	24145

I will have to manually adjust the Vee bearings on the X but hopefully that's not too much of a pain(instead of cam adjusters).
I hope this is an upgrade to the Z and not a downgrade!!
The bottom of the X has approx. 7" clearance from the bed after I add a whole base board and then a spoil board on top- gives me a usable Z height of 7"!! providing it doesn't have too much play.
Steppers, drivers , psu's etc all ordered- gone with a UC300eth - 5lpt for the control box
Water cooled spindle has arrived ,wow its got some weight to it!