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. Twin beds are 39 inches wide and 75 inches long, so a standard twin headboard is 42 inches wide. The twin extended headboard size is also 42 inches because the difference between the two beds is in the length. A twin extended bed is 80 inches long. The full-size bed, also known as the double bed, is 59 inches wide, not quite double that of a twin bed. The length is 75 inches.