Our Island Packet
is a 37 and has a 49'6" mast
instruments. We had no problems at all on our trips up and down the TTW. I think the min bridge is 52' but I could be wrong.
Of course, it's all motoring and you do get to talk to many towboats.
If you have never been down to the Yellow Creek area, on the Tennessee where the TTW begins, you might find that to be a good place to keep your boat. It would be fairly close to Nashville and Pickwick Lake is huge. And only 450 miles to Mobile.