I am about to pull the trigger on building a large machine, I need to know if anyone has experience with any caveats (the physics) of a machine this size. Is droop a problem due to the span of the rails? How about vibrations or resonance due to size? I am looking at it from the perspective of size, all else being equal (same belts, rods, etc...) I need to know if there is anything you encountered building a large machine that is important to know.

Thanks!!