Improving on a design deficiency

[Steve Bryant]

I have faith in the silver soldered joint. In my experience the base metals fail before the solder joint does and since the spigot of the extension protrudes into the original nuts internal hole by about 7/16" the soldered joint is around the spigot and on faces of the mating parts. 

To be honest I didn't feel like machining a new one from a lump of hexagonal rod.
Stephen