A couple of observations regarding Derek's angle setting jig:

If you are using a CBN wheel, you don't have to worry about the wheel changing diameters. Before it would ever be noticeable (a long time from now) the worn out wheel would already have been relegated to your scrap metal heap.

If you can figure out where the grinder's axis of rotation is (a lot easier after you have removed the guard and installed the CBN wheel, since you can then see the end of the shaft) a line drawn from the center of the grinder's shaft through the point where the jig's radius intersects the flat that rests on the tool rest is perpendicular to the arc and at a complimentary angle (90° - 25° = 65°, for example) to the flat of the jig.

Derek, if you can figure out how to make this explanation clear enough to the casual observer (in a non-accelerated reference plane), maybe with a diagram, you might consider adding it to your explanation in the article on your web site. If you don't have a CBN wheel, it's sufficient to approximate and mark the center of the shaft on the outside stone guard. You also might explain how you grind the circumference arc on the jig without filling the stone with scorched wood dust  ;^).