Common practice is the longer of your length from the tip of your anchor to the back of your dinghy or the slip you are in. Makes our 54 into a 58 or approx an additional $600 per season. In a past marina, I was charged for the entire 60 ft slip I was in. I can actually support one price per slip, regardless of the boat in it, but they would hit you for more, if you were over the 60ft in that case. Upsetting. They all do it.Sorry no idea, but it's kind of nifty that they fold up to save you a couple of bucks on dockage, in those places that include such things in the slip price. I've never actually been in one, but I hear there are places that are that greedy.