At sewing day on Saturday a member had a table center piece that she had made and marked snowmen on it with a frixion pen. After machine quilting it, the pen came out beautifully from the cream fabric with snowflakes, but remained on the cream solid fabric & would not come out no matter what she tried. She was busy appliquéing squares over them & will need to re-quilt that portion of the snowman. Both fabrics were 100% quilt shop quality fabric so it really doesn't make sense, however it sure would make me hesitant to use it on a large quilt.
Could you run a plumb line across with chalk & then stitch that row of yoyos on and once that is attached, measure out from it each time?
I have the blue wash out pen too, and find that if they are too old, the blue ink will disappear without being washed, not sure if it's because there's not enough of the ink/chemical stuff left in it, or what.