I searched a while no with no result, so I try to ask here:

when I install a linear guide with two carriages, is it an advantage for precision to connect them with higher spacing? (Let's exaggerate: if I have a 2 km guide and move 10 cm, the height will be changed very little at the 10 cm distance).

The connection will bend however. So there may be an optimum. And if it plays a role, is preload important?

I know that there is a waste of movement space, but if it gains precision, this may be worth it. One could even build a portal with flexible carriage spacing.