One thing that always scares me of ever running a metal spur is if something gets stuck inbetween it and the bell. Inside the tranny all the gears are protected, but with a spur it can happen. Just think about the damage you could do to everything by a nice size stone locking it up at that point. The motor will have to lock up or break the metal teeth off the bell or spur to take the load off unless you get off the gas and let the clutches release.