The Community of Disc Golfers and About All Things Disc Golf
For the sake of those you may have inspired with this really cool sign: Get permission first.
It's not YOUR home course, it's Saint Louis County's (or whatever government or private owner).
Adding anything to a park without permission is vandalism, and usually breaks the law.
No parks person I've ever talked to would ever allow anything to be mounted directly to a tree.
Take the required step of finding out what the park manager wants. Make sure that what you think is an improvement is actually best for the park. The final result will turn out better, and not be subject to being removed.