RRI? But of course.

I've also considered a "t" shaped thingamabob which could be inserted and then twisted. Problem there is whether the (obviously small) shaft would deform under torque before the dent came out. The dent, by forming a triangular cross section, has, to some extent "stiffened" itself. The brazed joint might be the weak link. Suitable clamping would certainly need to be applied. Possibly a series of ever larger-headed "T" tools could be employed?

The arsenal guys, having zero concern about reapplying a throatpiece, would surely have used the MANDREL method.

"Spandrel" is an architectural term relating to exterior structural glass, or opaque panels such as used in high-rise office buildings.