I want to add a passenger side mirror to my roadster. I took the windshield posts off thinking I could just drill and tap into it . Now I am not so sure, the back side of the post is welded to the front portion so I have no ideas what is on the inside. Is this normal? do I have enough meat inside to drill and tap to support the mirror or does it require a nut to be welded onto the inside. I would appreciate any information on this before I mess up a good post. Thanks