No one with the R/C has answered, so I'll reply based on my recollection from when this has been asked in the past.
It's a free ocean - you can certainly sail out there with the fleet.
However, when you are "tagging along" the R/C and entered racers know you're out there, and that creates some responsibility. If you need help it is likely that one of the entered racers will be your closest source of help. Per the Law of the Sea they will come to your aid. While they may request and receive a time adjustment for doing so, it may put them into a different weather pattern or otherwise compromise their race.
So the short answer may be "As long as you don't require assistance." And who can know that in advance?
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I won't pretend to answer for the RC, but I think what Bob says is generally correct, with a significant additional caveat from the OA's perspective.
"ghost participants" can inadvertently create huge liability risks for the Organizing Authority, if they are at all recognized, or if it can be shown that the OA was aware of it.
emphasis added to Bobs reply...
Basically, you haven't indemnified anyone (since presumably you wouldn't have signed a waiver), but by tacitly allowing you to sail with the fleet the SSS could be, in the eyes of an ambulance chaser, endorsing &/or encouraging your participation in a high risk activity should things go sideways.
I wouldn't say any of that precludes you from doing your own thing and sailing out the gate for a couple days, but I wouldn't talk it up or as Bob says "ask for anything".
For that matter I'd be cautious about where and when you time your "start", er, departure.
I really hate to be a killjoy.
It's a sad commentary on the litigious world we live in, I know.
Chalk it up to scar tissue from being deposed a few times for events that transpired at concerts I was managing (different context, but extremely unpleasant).
DH