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.
A standard twin bed frame measures 39 inches wide by 75 inches long by 7.5 inches high. A twin extra-long frame measures 39 inches wide by 80 inches long by 7.5 inches high and is more suitable in length for a single adult.