I’m using F&T now too with great results. Remember, with the 2 tube version, you only use two tubes when using 6v6s. There is no down side to building the 2 tube version, but no advantage either. Follow the single tube layout (and schematic) and you should avoid the vague details in the original (book) layout that has caused construction issues for some. Having already built a 5F2a, you should have no problems with the Two Stroke. Good luck! (Btw, wait until you hear what 1 good 6L6 sounds like).