This is my second one of these. I am changing the pattern to HDC instead of SC to help with the buckling and it is helping tremendously. I started with a starting chain of 96 (adding 10 to each side) and an extra 10 rows at the top and bottom in an effort to make the blanket bigger.

With these changes the blanket lays perfectly flat and is 26 x 32 before a border.

MY BORDER
(continuing with 3 sc in corners for rounds 1 through 7)

R1 - same as R1 of pattern border, (on the sides, for this round only, every 3rd stitch I put 2sc), turn to back side

R2 - clusters with 3 hdc between each, turn to front side

R3 - HDC around, with 3 in each corner, turn to back side

R4 - same as R2 but offset with the clusters inbetween previous row clusters, turn to front side

R5 - HDC around, with 3 in each corner

R6 - same as R5

R7 - same as R2 of pattern border

R8 - same as R3 of pattern border