I think rinko, in combination with an airline that is bike-friendly (no oversize charge), should mean it gets accepted. If not, you can politely and nicely say you packed it down small to take up less space, versus putting it in the typical bike box, which takes up a lot more room, and you did this to be considerate of others, because you would not have been charged for the large bike box. Put on your friendly face and communicate only the best of intentions.