Hieronymous, the 2006 article was heart breaking. Yeah, it's sad as hell for us musicians who travel via air. But in all fairness, the article was written back in 2006.
Again, we are talking about the size of something just about or equal to the size of an average guitar...
In fact just call it anything you want...
But just remember to ask yourself this question: will this bag fit the overhead locker and TSA baggage requirements...
Ask for the measurements.
Once you know the Airlines and TSA measurements, measure your bag.
If your bag complies with their rules, then at this point, walk proudly and enjoy your flight... (because you did your homework...)
However, if Flight attendants stops you while entering the plane, tell you know the rules and you would be more than happy to show that it measures perfectly for flight. (There's usually a bag measuring container, that validates size at most boarding gates) ask if they would measure your bag (work with them, make this a professional issue not personal).
If they still stop you, tell them it's a bag with a guitar inside and it could be easily damaged...
Tell them, most hard shell case wouldn't fit their overhead lockers, and the soft bag shotens the length to stow with ease.
Tell them you want to follow the rules... Stay professional and cool and please never make a scene. Be cheeful and smart. Stay on point, with the measurement rules, you have nothing to fear.
If they still want you to check the bag in, ask them why... If they just say because they say so... ask for an official statement of their bases for refusal.
IT WILL NEVER GET THIS FAR, BE COOL!
Last post on this one, enjoy your fly.