The problem I found is--if you have to cut much off, the log on the outside is smaller than the others. I would probably try to find out why the blocks are different sizes, probably your seam allowance isn't 1/4 inch all the time. With so many seams, being off just a couple of threads adds up to a big difference. Marking on you machine bed isn't difficult or expensive and a 1/4 inch foot is a great accessory. IMHO
Sue