After choosing the replacement square, I kept flipping through the book and found the following 8 squares to add to the afghan making the grid 4x5 instead of 3x4. I chose a mixture of blocks that are worked in stripes (3) and in-the-round (5).
Color A. Foundation chain of 38 to add to the length, meaning there are 6 shells in Row 1 instead of 5.
Color D. I repeated Round 7.
With colors D, A, E, and C as Eaton's A-D. I repeated rounds 9 and 10 after the first round 10.
With colors A, C, and B as Eaton's A-C. I repeated round 5 before Round 6.
With colors A, B, and D as Eaton's A-C. I repeated round 7 before Round 8.
With colors A, E, and C as Eaton's A-C. Foundation ch of 37. I added 3 sc to both the A and C sides of the grid and 2 sc to the B stripe. Total of 36 rows.
I made it with 9 granny stripes, but no extra width. The stripes color pattern is as follows: A, B, C, E, D, E, C, B, A.
With colors B, D, E, C, and A as Eaton's A-E. I repeated round 7 after round 8, followed by a modified round 9: sc in each dc and ch-1 sp with 5 sc in corner sp.
Here are all the squares laid out before joining, for which I used an invisible seam, but the pattern suggests a whipstitch.
My next (and final) post on this project will be about the border because I had to do some modifications due to the added length and width.