I'd probably use solid sashing and smaller pinwheels as corner stones. Your sashing would just need to be the same width as your pinwheel cornerstones. You could experiment a little to see what size pinwheel looks best to you with the bigger blocks. Then you don't need to resize your big blocks. I'd use a fabric that reads as a solid that would frame the big blocks and help them pop. The cornerstone pinwheels would still be scrappy like the big ones. I love the blocks you shared. The colors work wonderfully with each other in each block. Keep sharing your progress!