1/2 0f 100 (100x100 quilt) is 50", so you need 25 2" blocks to go from the center to the bottom and another 50" from the center to the top, so you are fine with 2 1/2" squares. You would need 20 2 1/2" blocks, so the 3" squares would be okay, too. If you go to 3 1/2" squares which is a 3" block, you can still use all your fabrics, but you won't see much of the some of them as there is only one repeat. I bet a TATW has an uneven # of blocks so one comes out centered, but this answers your question. I hope you are strip piecing it.