Originally Posted by PVDProf

I think only UA (and LH?) use the midfield, though, so other airlines would be OK at any hour.

In addition, you could do the rip-off trick with a bag that was arguably carry-on compliant (where the argument would be with TSA). That is, you could check a 22" case at an international origin, claim it midfield at IAD, rip the tag off, proceed through TSA screening into terminal C and then exit the secure area. But that might be hard with a 29" suitcase, and wouldn't work with a bottle of scotch.