With our five foot draft, it got pretty sketchy south of Channel Five. Lots of times the sounder was showing 5ft in the middle of the channel, but never felt a bump.
When we got to Marathon, I had a diver come to switch out some zincs, and when he came up he said "I see you came down on the inside.... your keel is niceley sanded for the first 4 inches or so" .
We took to either going in/out of Channel Five or just using Hawk Channel all the way.
North of Channel Five was not an issue, but I would check the LNMs and your towing company for local knowledge.