Sometimes my old brain will just not want to work, so I go back to the old ways. I draw the block out on graph paper, cut out the pieces and lay them on bigger paper. Then I can move them around until I find a workable size. Be careful because you could end up with really odd dimensions on the triangles. But adding borders and increasing the sashing should work. Adding additional colored borders will add a bunch. If you are looking at an additional 18" to the width and add 2 colors borders of 3", that already takes up 12" needed. And adding 1" to the sashings would give you another 8" so you wouldn't have to change the blocks at all. The bigger issue would be the length because you are looking at adding 27"! You could do the borders and sashing thing and add one more 'row' of blocks (so the sides were three wide instead of two wide). This would increase your length without distorting the pattern. Please post pix of what you decide to do.