Vancouver is a city on the north bank of the Columbia River in the U.S. state of Washington and the county seat of Clark County.
The width of the twin quilt is 66 +12 (for the two extra columns of 9 patches) + 4 (for the two extra strips of sashing) =82, which is a bit wider than your target of 78, but close enough. Plus, it's nice to have it a bit too large than a bit too small.
Twin Bed Dimensions. A twin size mattress is the smallest mattress available and is best suited for one child or one adult. The dimensions of a twin size mattress are approximately 39 inches wide by 74 inches long. Taller adults may be more comfortably sleeping on a twin XL bed size.