I went on Bonnie Hunter's site, quiltville, and she has a chart for setting and corner triangles. According to her for a finished 8" block, which is what your 4-patch would be, the corner triangles would be cut at 6 5/8". To make it FLOATING, I would try cutting at 7 1/4" or 7 1/2". Since the floating 4-patch is bigger, you want it proportioned correctly, IMO, so I would fool around with it. You could also cut your 4 1/2" squares in half and start with 2 1/4" squares, rather than the 2 1/2" squares. I think that would be nice too. Thanks for the link to the video. I liked her floating 4-patch. Easy and not too precise.