I made one and my seams are coming apart. You have only one seam holding the blocks togather and it is the backing fabric only. You need to shorten your stitch length and stitch as close as you can get to the blocks.
This makes a stiff quilt also so will not make another one.
I bought the rulers and the inside one is 7 1/2 in so it comes in handy when you need this odd size.