Flying with a poster tube as a hand luggage I am flying to a conference, in which I am presenting a poster.

In principle there might be a problem, as the poster tube:


is a second piece of hand luggage,
it is longer than the limit allows.


However, it seems that it works (once I tried with no problem, my colleagues usually have no problem).

Does it happen that one is not allowed to take a poster tube in the hand luggage?

If so, how to avoid this problem? (Advice, tips and tricks are welcome.)

If the question is place-specific, I'm interested mostly in EU.
There are a couple solutions to the "transporting a poster tube on a plane" problem:


Most flights allow a second piece of hand-luggage, so that bit is fine. And while it is larger in the length dimension than is usually allowed, I've never had this be a problem. In not-very-full flights, it can be stored on top or behind other bags. On fuller flights, I usually just ask a flight attendant for help. So far the tubes have ended up behind the seats in the last row against the bulk head, and in the coat closet usually reserved for first class. Generally, I find they give you "credit" for trying not to be a problem.
As has been mentioned, you can get your poster printed or shipped to the conference location.
Cloth posters. These are becoming more easily accessible. While more expensive than paper posters, if carrying a poster on forces you to check a bag, and your airline charges fees for those, the cost difference vanishes swiftly. These can be folded and stored flat in a shipping envelop or bag. Just make sure to take them out and iron them on a very low setting to get the creases out before you hang them.