[F22Rapture]

How would you guys prevent the chains from tripping the sensors? Because of the chains "dancing" afterwards, you would need to put them both far to the front or back... the back doesn't work because some low-velocity frisbees never make it back that far. You could put them both close to the very front, but then you wouldn't have much spread available.

Also, I've seen several points at which multiple frisbees converged to enter the goal at almost exactly the same spot and almost exactly the same time. A laser or ultrasonic sensor would have a very difficult time discerning this.

Also extreme wide-angle shots... you would possibly see a frisbee tripping multiple beams at once.

I think weight, despite its current issues, is still the best way to count frisbees.