To increase the odds of success, it might be worth checking it in at the curb (with a $5 bill visible in your hand). If the skycap measures it (which I doubt), just say "never mind" and go inside. The odds of BOTH the skycap and the Delta counter measuring the bag are infinitesimal, unless the bag is grossly oversized -- and yours isn't. (Whoops... I just noticed that you're based in Israel, so I don't know if this idea applies.)