@Colby something else to consider is thumb position. Generally speaking, the more the thumb is pointed up, the more bicep involvement you are going to get, especially on the down swing. As a guy who also injured his bicep doing swings, I make sure that my thumb is at least parallel, if not slightly downward throughout the movement. After I made that change, and focused on form throughout, I have had no other issues.
Either version of the grip, principle is the same. There was a forum thread on this topic previously, and that is where I got the tip. If I get time later I will see if I can find it.
I think Bunn is referring to the vertical grip where your thumb is pointed to the front on the bottom of the swing, and its pointed up on the top of the swing. It's not a typical grip used for swinging a single kettlebell. It's downside is that you limit the range of motion of the bell on the backswing, and theoretically you could injure you elbow by hyperextending it.Very interesting . Are you referring to the "hook grip"?