If you put 6 18" blocks on point, 2 blocks by 3 blocks, with plain blocks as spacers, your center would be about 50" x 75" even before adding sashing. Add 2-3" sashing, a few borders, and you quickly get a bed-sized quilt. LOVE big blocks! This is a great project, honoring your husband's grandmother, putting her blocks to use (wouldn't it be reassuring to think someone would do this for our UFOs?), and creating family heirlooms. Good luck to you in doing it, and we'd love to see the final result. If you don't chose to put photo blocks on the front, consider doing it for the back, with a little history of the blocks, their maker, and if course yourself, to preserve that precious family history.