That is a lovely pattern!
What size do you actually want? The largest size is a full/queen at 99" x 106". The throw size is 56 x 63. Because the pattern is rectangular, you want to keep the size proportionate. You could make the bigger quilt, then cut the top down to the size you want; however, this will alter the pattern somewhat since the white side triangles will become smaller.
Does the pattern have you cut strips of different widths for the different sizes? If so, I would simply adjust the width of the strips somewhere between the throw size and the queen size to get a finished size in-between.