Decide on a 'size grid' . For example all Blocks will be a multiple of 4 inches finished- 4 x 4, 4 x 8, 8 x 8, etc. Then cut all your T-shirts using that 'size grid'. Now you have to play. Count how many of each size that you have. Get some graph paper and an cut out that number of each size (or do this on the computer). Then move them around until you get a layout you like. Then fill in holes with either blank -T-Shirt fabric or your pinwheels and 4 patches.