Can you show how you are doing the math? I only tried the top part of the panel and it isn't working out for me. One thing I am not sure about is whether you are counting the corners. Here's how I did the math:
27-3/4" wide = 111/4ths = 222/8ths
4-7/8" squares cut minus 4/8" for seam allowances = 4-3/8th's finished squares = 35/8ths * 7 = 245/8ths
Already my math doesn't work, so I quit there. It might work differently if you are doing the sides first, then the top.
I think this is doing it the hard way. It would be easier to add a border all around the panel (making it extra-wide) first. Then cut the squares the size you want, sew them together to fit a side, then trim the border to fit the strip of squares. Basically in this case you are making the panel fit the squares rather than trying to make the squares fit the panel size. Adding a border to the panel allows you to adjust the border to fit the squares.