Why not just allow them to put a green tag on your bag and then take it on the plane anyway? (The GA doesn't follow you down the jetbridge...) I often do this with a Wenger rolling computer bag, which does not look as if it will fit in the overhead of a CR2 or an RJ145, but will in fact fit perfectly well if you put it in head first with the wheels facing out. That doesn't work for standard rollerboards, though.