Re background fabric quantity: these estimates are good. With this quilt the pieces are small with some having more fabric on the underside in seam allowance than what shows on the top. The method used also effects the quantity. With hand piecing, since one sews seams "on the line" seam allowances can be scant. Keeping a 1/4" is not as critical as sewing on the seam line. To the other extreme foundation piecing uses larger chunks and then cuts to size producing waste. Over a quilt with so many individual pieces the differences add up.