re: Hardwood floor inlays - Walnut in Oak

Steve, all I can say is you've got nerves of steel to put a spinning router to a newly laid floor. If I were to try this - and it's most certain that I never would - the existing hardwood floor would be drenched then cupped from the sweat off my forehead. 
Needless to say you did a fantastic job here, it looks magnificent. It really adds beauty to the floor, one grade A job well done.