But I didn't get any staining done until I gave Uncle Dave a little tour of the house...
After getting out of the secret space, Uncle Dave wanted to walk down and see the goings-on at his parents' former house at the end of the lane (where he grew up):
Of course, the diamonds I drew to guide the floor staining couldn't be just normal ol' diamonds...that might be uninteresting. I decided that I would try staining in the dark walnut color, leave it sit overnight, and then stain the entire floor dark walnut the next day to 'tone it down' a bit.
Life is an experiment; be conscious of what hypotheses you make.