First thanks to all for their prompt responses.  Several people suggested
carrying garment or suit bags which are hung up front when boarding a plane.
I saw people putting such bags in a compartment in the front, but it is
completely unclear to me how they got on board with such large items in the
first place.  I had assumed they were traveling first class.  Few people had
these things on the small carrier I used.  I even had trouble with my
suitcase designed for air travel, the space under the seats was smaller than
I had seen before, but it has been awhile since I've flown.

As for charming the people, the man in Nashville was simply set to not
respond for any reason.  I was as polite as possible, he gave me a box to
put the poster board in cargo.

Catherine Sexton mentioned fidelity folders, meadowcote and kraft paper, and
I don't know what any of these things are, I would e-mail you directly
Catherine but perhaps others are wondering what some of these things are
also.  I can't envision how something held together with cloth tape would
have the strength to hold itself up.  The posters were required to be
free-standing.

                                        Thanks again, Miriam