This is exactly my view. I always travel with a duffle bag that is oversized but will fit under the seat. I always have it behind my back so the agents can't really see it without looking. One saving grace of every Wizzair flight I've taken is that they're always late so agents are more concerned with getting the aircraft out. That said, I wouldn't be too upset if I was asked to pay the fee. Split over all the flights I haven't had to pay, it would be low/flight!