5 - 10 years ago while working with music festivals, we started to get approached by building unions etc about OHS on the site. Our response was to formulate our own OHS guidelines, that were specific to what we did - ie set up and break down a site. It took a number of years, but I think it's a whole lot better in the long run as we are not being dictated to by unions that really don't understand what it is we do.
The point I'm trying to make is that maybe the SUP clubs should start to formulate their own policies/rules/codes for these type of activities - that way, when other associations attempt to blanket us with some form of regulations, that may not be relevant to what we do, we are in a better position to deflect them by arguing that we already have our own code of practice in place.
I'm far from being an expert on these things, but mikeman has made some excellent suggestions and I personally think that formulating some guidelines on the SUPvic website, for example, on downwinders as being proactive step. Similar has been posted on this page:
www.supvic.com/buysell/