Reacher is all about attitude. Just because he happens to be 6 foot 5, doesn't mean that no-one shorter than that is capable of playing the part. When they cast someone as a character from a book, people will always say they're wrong for the part. What are the odds of finding a good actor with the exact physical characteristics as the character in the book? Arnold Schwarzenegger is 6 feet tall. Would anyone say he wasn't big enough? You can't please all the people, all the time. Remember all the moaning about Daniel Craig being too blond to play Bond?