Well, you will have the measure each wheel.
This is a Fly Classic wheel sized for the 15x10 CB Design. I measure the depth of the wheel, then that dictates my cut. I always cut a little proud and then hand sand the insert on a flat section of sandpaper to set it just right.
This is another example. Scaley MGB.
Not sure if this helps or not. Getting a digital caliper with depth gauge is a great tool. Lowe's has small ones for about 20 bucks.