Well, I re-read this thread and it looks as though you had already found the solution to your problem. I wonder how many people don't understand the importance of a scant 1/4" seam, or even what it is? The issue you ran into is a good example of how much it can matter in some situations.
I also wanted to say that I went and looked at this class on Bluprint, and the block was challenging for some people--so much so that a couple of people just gave up. You did an outstanding job considering how many pieces there were. There was a lot to keep track up. It's awesome that you persevered in figuring out how to make your block perfect. Kudos!