I have been through the CBBT many times. My 5-er is 13'2", and I've seen many tractor-trailer trucks going through. They always ask me at the toll booth if my propane tanks are shut off and I usually stop (on the side) to make sure they are. It is narrow and there's not much room to spare if you meet a big truck coming the other way in one of the tunnels. I just keep both hands on the wheel and take it slow when I need to!
John & Janet from Connecticut
2012 Keystone Montana 3150RL
2012 Ford F350 Diesel 4x4 Lariat Crewcab SRW