oops ..

the problem now is how do i do the Z axis

mount the rails so that they move ? or mount the bearings so that they move ?

i realize that mounting the rails so that 'they' move is better as the forces on the rails are consistent and that the bearings are fixed ( as per the drawing) and .. that the bearings are maximized as they are directly bolted ontop of each other

but ... the biggest problem is that the travel is now limited ....

if i google z axis pictures, the majority is showing the rails fixed, and the bearings moving ... is it really worth the effort to do the visa versa ?