Good idea! It might make the center assembly even more of a monster than it is now though. I agree with Vicious on the magnification of surface flaws. Right now it is no big deal to have slightly warped conduit, especially if it is only slight across the whole length before cutting, but with 3 stacked against each other they would have to be perfect or the fit would have to be intentionally a little more loose. Maybe a spring mechanism to push the bearing against the rail, but allow it to push back if something is warped or otherwise imperfect in an area. Kind of how an extruder could allow for an inconsistent diameter of material through it without a problem (physically speaking. There would be issues with too much or to little filament in a print).