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.
Bedspread and coverlet dimensions (approximate): Below are approximate bedspread and coverlet dimensions (width x length) to accommodate standard mattress sizes (may vary a few inches in either direction): Twin bedspread - 78 x 108 inches. Twin coverlet - 68 x 94 inches. Full/Queen bedspread â 96 x 108 inches.