okinawa77 said:
[...]if I were to shoot the CB into the rail with follow, it doesn't "double the rail", but if I hit an OB near the rail with follow, it does double the rail.
No offense, but it will - and can double the rail. The key is the amount of force the cue ball relative to the amount of spin it has. The object ball removes most of the speed, but virtually none of the spin.
That is, if you shoot straight at the rail with top, the speed of the cue ball will be too great for the spin to force it to double. In your example, however, the CB hits the OB and loses most of its speed - and then it travels towards the rail. The amount of spin is high, but the amount of movement is low. This enables the cue ball to hit the rail at a slow speed such that the spin can take over. You can replicate this, as you indicated with the masse shot - which pushes the CB into the rail at a slow speed with lots of spin.
If you changed the angle of your shot (hitting thinner), with the same exact stroke and speed, the cue ball would not double the rail because it would hit the rail with so much speed that the spin could not bring it back to the rail.
Lastly, if you shoot this shot hitting the cue ball almost full in the face, you can achieve top-stop. It is a matter of spin vs "speed."
-td