Has anybody flown Icelandair with the Rick Steves carry-on backpack? Looking at their website, their carry-on limit is listed as 21.6 x 15.7 x 7.8. The convertible backpack is 21 x 14 x 9. Is that extra 1.2" of depth going to cause us a problem? I know it's squishable, but just wondering how particular they're going to be when I check in at the airport.