Update

It's been a while since anything notable's happened.  I transferred the Guinness clone to secondary, and added the Jameson/Vanilla mixture.  The finished product smells amazing.  I can only imagine how much better it will be after allowing the flavors to melt together.  I tasted some of the base stout before adding the whiskey, and it tastes identical to Guinness.  The folks at Austin Homebrew really know what they're doing.