Oh, sorry I forgot to address the questions about the pattern. The original pattern photo was shown in the Martingale blog. The designer is Pippa Eccles Armbrester. You can find her on Pinterest. I drafted her original pattern and then modified it to fit what I had to work with, which involved some set in seams and tricky piecing to make that odd sized upper left corner work out the way I wanted it. The original is simpler and easier to do.
As for fitting the squares, all you have to do is make sure that the sizes of your next size down when combined equals the size of the large one next to it. For example, My medium squares finished at 6" (cut 6 .5"), so the next size down = 4P of 3" finished (cut 3.5")= finished square of 6". Now to finish the next square down at 6" also, or I can finish each one at 3". A finished 3" 4P needs 1.5" finished squares (cut 2"). So, I'd need 4 of those to = the 6" finished block. I opted in this case to do lots of short strip sets and make 16 Patches. I used 2" strips to make finished 1.5" squares in the 16 P. I would be happy to send a photo of the graph I used as my pattern if anyone would find that helpful.