Did you measure your quilt before putting it on...a lot of times the quilt will be a bit bigger on the ends than the center. Do you baste down the sides before quilting as you roll. That helps... I may go ahead and put measuring tapes on both my leaders. I tried the painters tape and it helped me eyeball it, but if you want to make sure it's staying consistently the same all the way through the quilt, remeasuring and basting it to that measurement as you go may be a good idea.