Rick,
As you can see even my good friend (Santiam) and I have minor differences of opinion.
So for sure you need, good clean arrow flight, a reasonable weight arrow and it really, really helps if you shoot them low.
If you can have the mental presence when a bull charges in...aim for the top of his heart. A hit a little low is still great, too low and a clean miss, high and you are still ok.
They can cover a huge amount of real estate in a heartbeat and a good bloodtrail only helps your cause.
Good luck!
Bob