Hi Chris. Awesome progress! I would recomend a layer between the diagonal boards and the hardwood. If you are using a lot of shorts and ends there will be a lot of boards not spanning 2 boards. Also the diagonal floors tend to be of slightly varying thicknesses and with the cup of the boards facing different ways. All of that adds up to squeeky floors. As mentioned above screw everything down with deck screws. If for thickness sake you can’t put a subfloor screw it all down and rent a floor sander the large belt ones not the round ones to knock down the high points and irregular stuff on the diagonal boards. Just some thoughts from my own screw ups over the years.