I've been fighting the chair/umbrella war just east of 30-A in bay county for years. I once had one of the beach services actually MOVE my stuff (not in a nice way - read: they TORE MY STUFF up). I had gone down at 6 am to set up (have to in order to beat the service folks) and then back up to change, get coffee/kids, etc. In my 40+ years on earth I've never had the police called on me, but that is exactly what happened. Funny thing is, the police agreed with ME when they got there. Beach service folks had to give me cash to pay for my stuff they tore up. But who wants to FIGHT? That just ruins everyone's day. (This was in PCB proper about 7 years ago).
In 2012, when we bought our condo, one of the reasons we bought at Pinnacle Port/Carillon was for the very fact that there was so much open beach area and we wouldn't have to fight rental services for beach (although during peak season it's still a rush to see who gets the most "convenient" spaces - i.e., by the walkways, lol). I've since made friends with the service folks and we have a pretty nice agreement about allowing space for people with their own stuff. Just talk to them - they can be reasonable. In our case, we agreed that leaving space between chairs for "first come first serve" was appropriate, with the exception of extremely heavy holidays (Memorial Day, the 4th, etc) in which I agreed that we DIYers leave the umbrella service folks a bit more prime real estate since they tend to really be full those weeks.(Since I am always down at 6, I seem to be the one that "sets" the tone for the DIYers on where to set up - inevitably, I get my stuff up first, the service folks set theirs to the right of mine and that seems to be the dividing line for the day). Seems to be working for us. Again, just talk to the service folks. They can be reasonable.