Previously I'd extracted the sheared bolt from the 2nd piece of profile. 2 more to go. At this point, I've gotten to an approach that works reasonably well, counter sink the hole, use the M12 tap to tap the hole, then install the insert. The larger tap wrench and long handled wrench make this easier, but its still a workout. The main thing to watch is that the tap is kept square to the profile, and the insert is kept square while installing.
