I know (hope) my strips are the right size as I just bought this new thingy to cut them with tonight - Shape Cut Slotted Ruler, by June Tailor. This thing is really neat! But I have never had a problem with my allowances before. I got two rows done, sewn together in rows, looks good except for the last square, it's off almost 1/2"! I gave up on it for tonight. I'm making it for my grandson's birthday, which is the beginning of May. Good thing I have plenty of time to get it figured out! lol!!