I will usually add .020" to the diameter of the bullet for my taper crimp (and a bit less due to variation in case wall thickness depending on the head stamp). So for .451" diameter jacketed/plated bullets, I will use .471"-.472" taper crimp. For .452" diameter plated/lead bullets, I will use .472-.473" taper crimp. Depending on the case wall thickness, .020" added to the diameter of the bullet will either result in flaring returning flat against the bullet or slight taper crimp that indents the bullet.
Drawing not to scale:
