Robin, how would you support a round rail with a linear bearing that fully encloses the rail?

these are 16mm carbon steel rails supported at each end - according to my calcs a single rail will deflect no more than 0.04mm under a 35kg central point load and a) I dont plan to load them that much and b) the load is distributed across two pillow blocks on two rails so expect the deflection to be <0.01mm...

Where's the flimsy bit come in?

Irving...