Hi ellent,
I also like my seat back up straight and had a problem with the forward angle of the head restraints on my Edge. Initially, I flipped the head restraints so they faced backwards, but that seemed to defeat the safety objective by having a much larger gap between my head and the restraint. Eventually, I removed them again and made a very slight bend in the aluminum shafts on the restraints, immediately where they exit the restraint itself, to reduce the forward angle. Now I have them facing forwards again and they still slide up and down, but there is a little more room between my head and the restraint, which allows (for me) a more comfortable driving position.
I'm not suggesting that this is a great solution and I'm sure there are reasons not to do it, but this adjustment worked for me and the head restraints never bother me now.