Changing the k2tog-tbls (and similarly placed k2togs) into ssks.
Decreasing before the centre pattern (and increasing after it) so the 9 st border lines up more directly with the 16 st centre pattern. For this version, the border chevrons are aligned with the centre diamonds.
Adding partial repeats to make the overall pattern more left-right symmetrical.
Adding another repeat of row 15 (as row 27) to finish the topmost diamonds in the centre section.