I am restoring an old touring bike and decided to switch to an indexed drivetrain. I bought a pair of dura ace shifters from a friend, but I'm have a little trouble with the install. Firstly the DA shifters use an M5 bolt, but my frame uses a smaller screw. But this will be trivial to swap. The second problem is that their is a gap between the frame and the base of the shifter. The below pictures should illustrate the problem.









It looks like the shifter is designed for a boss where the flat part goes all the way down to the larger studded circle. Instead my boss goes flat then round then wider round with stud. Should I file down the boss?