Dunster, your avatar turned out better than mine did. As for backing, use the 44/45 fabric. Be sure to always trim off your selvages in the middle, press it well. When planning the measurement for your quilt top, if you can, make the seam go side to side instead of from top to bottom. When your longarmer ( from experience) will appreciate you a little more. The center seam can cause issues on rolling the quilt on the bars. There is such a versatility in your 44/45 fabrics and as said above, it works great.