You're quilting! you can do whatever you want! I have done it and none of the folks who were given the quilt complained.
You'd need to piece it any way if the quilt length is 45 and the fabric strip is 44. There's a little thing called 1/4" seams that will shorten the sashing. If it bothers you, put a contrasting corner stone in at each end of the sashing to make it fit. One other thing to do that is fairly easy, is to add a rectangular strip on each end of all the sashings. use one of the fabrics in the quilt. it looks cute. The rectangular strips should butt up to each other when you have them sewn on.