Thor, or should that be Zeus?

[Chaz]

Theoretically the bearing blocks should be bolted to the gantry and the rails to the bottom of the bed. If you put the blocks on the bed you introduce unnecessary overhangs and add a lot of metal supporting rails that does nothing. It should be more A frame and less triangular. OTOH, what do I know? -freaking smileys don't work-

Just to confirm you are referring to swapping the rail and cart here on the Z Axis?