My LOA is 58'3", but remember, the pulpit was added on, as was the swim platform. The pulpit adds about 3 feet, and the swim platform is 4 feet (nice!). So, that makes the overall space I take up to be 65'. Yes, I'm a 58' boat.
My marina has a rule that you cannot stick out of a slip more than 5' beyond the pilings. So, here's what happens....although my original docmentation says I'm only 58', I need at least a 60' slip to stay within the rules. So, I pay for a 60' slip. Truthfully, I think my pilings are actually set at 65' because I don't stick out beyond them. If I did, I'm sure the marina would be charging me for 65 feet.
Also, often if you take a certain size slip, say you put your 55' boat in a 70' slip because there isn't another one available or you just like the view from that one better, well, then you pay for the 70' of "real estate" you're taking up. Afterall, they could sell that slip to a 75' boat. The marina will never short change itself.
For my diver....I tell him I'm 53 feet at the water line because that's what he's cleaning. I don't think I should pay him for the part of the bow that raises out over the water, nor for the pulpit, nor for the swim platform.
All of this seems fair to me.