I did Dover too!
I left about 7am when all was quiet...except my thru-hull exhaust

It was flat as a pancake then but I know what you mean about the rough in the late afternoon. I came back at about 3:30 and hit the same crap you did. Not a fun ride at all as it was short and rough!
I found the ramps to be full of weeds and not very friendly. The parking Nazi was there in a heartbeat to capture my fifteen dollar tax for loading, but there was no one there to assist me when I came back. All four of them were sitting on their asses looking at me trying to manouver in the heavy wind!
Bumped the dock a bit, but no damage to the boat.
I figure about 6-7 thousand boats possibly? What's your estimate?