Will, that is good food for thought (pun intended)! Have not thought about the triangular void before. Where do you use your v gouge? I was also thinking of the same tool to create a diversion trench on the upper side of the brace before entering the post. Like a V that sheds to each side.

Mike, yes exactly like that! No chiseling required as the makita mortiser chain cuts on entering and leaves a nice true facet where it matters!