Help making a on-point quilt bigger by adding rows
So I can do math through Trig easily, but this math is stumping me. My mom found a pattern for a quilt that has square blocks set on point without any sashing between the blocks. The finished quilt measures 50x60 and doesn't have a border. Each block is 7.5x7.5 and has a hypotenuse of 10.6 inches. There are 50 blocks in the quilt, with the added edge triangles.. The quilt is assembled on point with 10 rows - the first row having one block, row 2 has 3 blocks, row 3 has 5 blocks, up to rows 5 and 6 having 9 blocks, then decreasing from there.
She wants to increase the dimensions of the quilt to 63x90 for a twin bed. We can add borders to help with the dimensions. She can either make the squares bigger (the squares are assembled with 4 squares, 2 short rectangles, and 1 long rectangle) or add rows. I'm thinking adding rows would be best to keep the visual interest of the pattern. What I can't figure out is how many rows need to be added to increase the 50x60 quilt to close to 63x90 (with a possible border)? If this was a quilt with set regular blocks, the math is simple, but with the blocks set on point, I can't figure out how many inches each additional block adds to the overall dimension of the quilt. Any help you can give me would be appreciated!!