consider making them a size that would fit evenly since you are going to duplicate them anyhow.
do they have to be square? would rectangles work just as well?
you might want to use a soap type of solution to position the squares as you are applying them.
since I used jumbo sized squares it wasn't necessary to do this. I just tapped the corners in place as I got them alligned..have to watch so that you don't overheat because the straight edges will buckle....can get tricky...lots of luck to you...I'm sure you will do well.........try doing a sample on a test bed.