Not being critical, (maybe I'm misunderstanding) but I question the idea of mating a tapped fitting to a tapped base. That doesn't allow the two parts to be pulled together any more tightly than they are at the position you start the threads into the base piece. If the two threaded pieces weren't tapped together, then the base thread is not likely to start precisely where the other fitting thread ends, and they will never be tight.

I'd thread only the base, and make the hole on the other fitting large enough to allow the bolt to move so the head can tighten the fitting.