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.
While sizes may vary, most lap quilts measure between 36 inches and 48 inches along each side. A 36-by-48-inch rectangle is a standard lap quilt size, as is a 36-by-36-inch square. Materials Using a good quality cotton or wool batting makes a cuddly, warm quilt without adding too much bulk.