I already had enough darks. The lights I had weren't true repros, and I felt they were too light (too high contrast). A quick trip to the shop changed that. Here are the lights and darks for the first 3 months.
I figured out that 1 metric fat quarter (FQ) will yield about 64, 2 1/2 inch squares. I will need 60 for the darks and 48 for the lights. So one FQ of each will do for the swap itself.
But how about - 12 for the swap and 12 for me? That means 1/2m of each.
And here's the twist - the swap blocks will have 5 dark squares, 4 light squares - the ones I keep will have 5 light squares and 4 dark ones.....I have a plan!!!