so, i did it, and have this pertinent info for folks considering it.
fyi, i used a black plastic serfas box, with wheels. it did not say bicycle on it.

on the way there, i checked it at DCA on delta, no questions asked, no problems. the security guys recognized it and asked. i said "shhh.... i don't want to be charged."
"oh, don't worry about delta. they usually don't charge. It's American and United over there that always charges people."
FYI - not recommended that you walk 9 blocks through a city with wheeled bike box. big pain.

returning, i had a hassle.
"is this a bike?"
"no."
"what is it?"
"trade show equipment."
"well, it's oversized, so we'll have to charge"
"no, it's under 50 lbs" (Actually, the case was so heavy, it weighed in at 48.5)
"but it's oversize."
(guy walks into office. talks to his boss. returns)
"What did you say this was again?"
"trade show equipment."
"and it's not a bicycle?"
"no."
"what does trade show equipment mean?"
"it's a display for at an expo."
"ok." (leans over desk looking at my other bag. presumably looking for a helmet.)

notes:
- if they do open the box, i'm told that you should point out that it's not a bike beacuse a whole bike would have brakes and gears. thus it's bike parts for sale at a trade show.
- $75 is the one-way charge for a bike usually.
- why the hell is "trade show equipment" cheaper for them to transport than a bike of same size, weight, and packaging? this is such BS!