Hey, what do you know. It says right here

http://www.cbp.gov/xp/cgov/travel/pl..._fee_decal.xml

that I need one because my boat is 32 feet. If I don't have one, I have to
fill out an application and pay the fee upon my re-entry and they will mail
me one.

Lesson: Don't believe anything you are told by phone when you call a US
Agency. Can you believe it?

--
Roger Long