You don't have to grind that much off. When I cut a tack I only cut it half way and hit it with a hammer. With the size of tacks I saw in the pics just a line 1/32-1/16 deep would give them a weak point to break at.
I was thinking about doin this but I think I'm goin to try it with a twist. To me it makes more since to braze the joint. If you do it right the braze will fill the joint and act as a brass bushing. It's not as strong as a tack so it should allow the joint to slip if a head on collision were to...
