My mother made quilts without all the problems of a "scant" 1/4 inch. Therein lies the problem. Seams used to be pressed open. Now we are pressing them to the "dark" side. IMHO, I think that all cotton thicknesses are not created equal! When pressing seams open they are more likely to be even when using the 1/4 in seam, especially if you use a presser foot with a guide on it. When pressing to one side due to the "thickness" of the cottons and if the seam is not exactly a "scant", you have a bump over 2 layers of material when pressed. Trying to figure out the "scant" has been trying but I am getting closer, I think? I recently read of a quilt designer/maker returning to the open-pressed seams because of all the problems with the "scant". I think a "scant" is in the "eye of the beholder".....just a thought... (sorry to be lengthy)