Your 2 7/8" square should work. Remember that your SIL probably hasn't seen the video or magazine, so as long as you pick a consistent measurement for the accent squares, you will get the 'look' of that quilt. Having said that, unless you are doing raw edge applique, I think it would be way quicker to just piece the flippy corners.
Best wishes for your SIL speedy recovery.
Last edited by PaperPrincess; 11-09-2014 at 05:35 AM.