Diamond Candy seems to be a Jewel Box variant. I think you can adapt it to 12" blocks by playing with sashing ideas. There are too many different blocks named Double Pinwheel and I don't have the magazine so I'm not sure which version it uses. Can you upload pictures of each block and I will see what I can come up with? The math may not be odd numbers--it may be just a matter of turning 1/4 inch into 3/4. It depends on the number of rows in each block as well as the shapes. Paper piecing can solve the odd measurement problem on some blocks also.