Just flew back from Amsterdam with Aer Lingus - because flights were full both going out and returning, they measured the cabin bags and quite a few had to go into the hold. These included the standard cabin bags used by airline crew (there were 8 of them on the flight out - Emirates, I think). The difference between AL and Ryanair is that even if the bag did not go into the measuring frame, it was just loaded into the hold with no extra charge. I think this may only apply to flights which are full resulting in minimum cabin storage. Be careful with those 'cabin baggage' cases which expand - if you fill them to the full expansion, they won't go into the Ryanair measuring frame.