I figure this is obvious, but since no one has posted yet...
RogerB, my understanding is Bradness is talking about 12 inches of LINEAR weld metal. There is no way I can think of you can fill the entire bar mount to strut surface with weld metal (Unless you whip out the JB weld...

. You have to go around the perimeter, so 12 inches would be the perimeter of the mount...
But then again, I didn't design the bar...