I saw this post and wanted to give a reference for the event as I was able to attend last year (to watch). This event is an awesome spectator event as the Karate action is based on "knock-down" rules without padding. While hand techniques to the head are not allowed, there are is tremendous action with kicks to head plus hand and punching to the body.
For fighters, this is a truly great Karate event. The organizing body is Enshin, that run the full Sabaki Challenge out in Denver, perhaps the premier contact karate event in the US.
Hopefully, I will be able to go again this year.
Kinge (who is not part of Enshin, Sabaki, or anything related)....