@slalom_frog...My club is using an EZ slalom course that we've had in for over a year now. Though I have not personally seen the anchors, I'm told we have a small block motor anchoring one end, and the drum brake off a dump truck on the far end. I do know that we use a come along between one set of 55s and the engine block. It seems to work pretty well.
Our lake is fairly sheltered from the wind, but we do have the occasional significant water level fluctuation, since we are at the mercy of the USACE (Corps of Engineers) and their flow management of a nearby dam. This sometimes results in us using the come along to adjust course tension. This is only really an issue once or twice a year. If we know about it, in the past we've sank the course by removing all buoys and letting it settle to the bottom. Maybe you could get away with this on your public lake? When the water level returns to normal, we drag a crazy looking hook contraption made out of rebar across the width of the lake to snag the mainline. We pull the mainline up and go down the line replacing buoys. This year, we didn't sink it in time, the lake flooded, and became one with the adjacent river. This ended up snapping a few arms, which we had to rebuild. To be fair, the arms broke from the current strength of the river, not just the rising water level.
Long story short...We use a come along and it works well!