Horizontal would give more surfaces to cool, as in "all heat goes up", only thing I can think about. Same with CPU coolers, Horizontal would be better. Naa, to slingshot a rotating object you need a force-point on the rotating object that points outwards the center and gets larger, bigger or what ever. Problem is that you get a dead point in rotation that needs to be compensated, like a drive stain (crank) from a bicycle. By the way, don’t pay attention what the factory says, that just to sell more dives after warranty periods . Platters are thick and heavy indeed, so they maintain continues speed easier then a lightweight plate, like the flight-wheel on a car-engine, lighter will stall the engine faster but spins up, revs, faster. (And that’s NO joke! ).