I took a look at Norwegian's limits and they are: 1 carry-on bag: max. 55x40x23 cm. I looked at other airlines and they all seem to be around this size and the ones that aren't (Ryan Air) are airlines I can easily avoid.
So it's over by .5cm. I'm wondering if this will work?
FWIW, we just did four Norwegian flights, two across the pond and two Air Shuttle within Europe. Nobody had their carry on bag checked for size. I'm guessing that since they are not doing well in terms of profit these days, they may not be interested in hassling their customers like they used to.