Here's why it was such a "stressor" . (self induced)
It was the nit picking and fine tuning of each individual board end and shimming them up so they were all equal and parallel. Once that was done, I cut the groove. Making them as accurate as I was able to do allowed me to make the edge look better.
I made the header piece end up a few thousandths of an inch or so
taller than the floor....... maybe the thickness of about 3 recipe cards This allowed me to leave the header with it's microbevel, and the cut board ends with
no microbevel. It looked much cleaner that way.
I didn't do any face nailing. I used globs of Bostics Best and 6 narrow headed casing screws to hold the board in place as the adhesive sets up. The screws were not "wrenched down" tight. Just enough to pull the header board snug against the existing flooring.
Decided a picture
with 1000 words is better than one without. I think it's self explanatory.
.............and no, ...........the board ends were
not as wavy as the ones in my drawing. A little embellishment goes a long way to make a point.