I lay the bow on its side and trace the curve of the back, unstrung, before I start tillering. Of course if it's is a board bow, then I have drawn, pretty much, a straight line. After bending the bow on the long string, or after immediately after un-stringing if it has been braced, I retrace (overlay) the curve again, in order to see precisely where along the limb the set is occurring. It is not enough to just gauge the overall string follow from the position of the tips. Knowing just where the set is occurring tells you much about where (or not) to work so much. These tracings are especially helpful on a stave with natural humps and hollows, but the technique works equally well on a board bow with working limbs that are not equally strained throughout. Assuring that the set happens where you want to, helps you optimize the design. Some will advocate for more set further out on the limb, rather than close to the fade, although with a short working limb like the mollegabet, having the set evenly distributed along the working limb might be the best you could hope for.
I use freezer paper taped to a piece of plywood, with two fixed stops for the tips and use a circular gage block with a sharp pencil to follow the limb.