I don't have the Stealth but I do have that size in the Limbo range. It is significantly (visibly) larger than my Salsa Air IATA trolley. Even if I could get it on-board I think it would be 15-20 kg when fully packed, which is not permitted by the carriers I mostly fly. BA's size and weight limits are very generous compared with the majority of (non-US) carriers these days. It's interesting to hear that others haven't had problems with carrying on this sized bag, but I agree with alpenrose that anything bigger than IATA size is a risk if, like most here, avoiding check-in is important to you. So I use the 56 as a small check-in case rather than a large carry on.