I have had it happen several time from a friend. She lays her quilts and backs on the bed and measures that way, well when I get them, the quilt top is always at least 6-7 inches larger both ways than the back. She also pieces the back and then it is too small too. I have tried, to explain, and asked for 8-10 inches more that usual, but it still is an issue. The last time she wanted a quilt basted for hand quilting and I sewed an piece of muslin to the bottom of her top, then she could figure out want it needed. At least I have caught her shortness earlier than I use to. Not so much work for me.