you'll definitely need to do something. they won't be "just fine" with a 7mm difference. odds are you've got a binding that allows for the heelpiece to have forward pressure adjustment. assuming that the heelpiece wasn't positioned all the way forward when mounted it should be able to compensate for that 7mm. just take 'em in to you local shop if you're unsure how do make the adjustment. or ask a buddy who's familiar with it. it's really quite easy, but is also very important to have set correctly.