I went ahead and made a gizmo after seeing Pat B. using one. What a great little tool!
Simple, effective, ingenuity
It's definitely designed for a flat belly bow, it was hard to keep it on the ridge of this round belly ELB.
I came up with a self centering mod.
If I were going to make more of these style bows, I would figure out something more permanent.
The other mod I would make to the gizmo is a different marking device. Don't like that the distance the pencil protrudes out the bottom changes as the lead wears away. A non-permanent roller ball pen would work, just have to figure out how to adjust it.