Edited to add: in my earlier post, I assumed that the panel actually measures 42.5 inches, allowing for 2 1/4 seam allowances. If the finished size of the panel is actually 43.5 inches, then you will almost certainly want to add a skinny border to the panel to make the math easier. To determine the finished size of the blocks for the length of the pieced border, divide the finished size by 12.