how close should window switch be to rev limit?
 

Whats the rule of thumb for setting the top of a window switch? Say if you rev limiter is at 6500, what would you set it at?

Depends on if you're an auto or t56. For a t56, I'd go about 200 rpm lower than rev limiter. On an auto, I would shut off based on rev limiter. I'd shut it off 100-200rpm before the car is set to shift.