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 twin model is 39 inches by 75 inches and typically works best in a smaller bedroom, on a daybed or with a bunk bed set. While it's possible to have two sleepers on a twin size mattress, it might be too snug. A twin size mattress fits in small bedrooms where space might be limited.