In process right now for better or worse. Pain in the butt. Despite being able to hit the specified dimensions between the two rails, and verifying that they are perfectly straight and parallel, existing underlying rivets (AD 470's) at the back end of the rails conflict. By that I mean that even after drilling out those rivets and installing flush blind rivets underneath, that there is now no room to install the #5 rivets without hitting the blind rivets underneath or having notable edge distance issues. Maybe it's me, but on the surface it seems like mediocre engineering.