I have been trying this off and on the past few visits to the room again.
Tonight I bested my prior best of 5 with an 11. Furthermore, I had many 6's and 7's. It just started coming back straighter than before, and really built my confidence.
One thing that I learned tonight, is if I get "slightly" out of line, I can get back in line by cheating the pocket, but using NO spin. Before, I was trying to cheat the pocket with spin. This only works if its out of line like an 1/8"... but it is very controllable. In fact, several times I bounced back and forth between being out of line on opposites sides of the ball, on successive shots. But it was controllable and I could get back to straight in.
After I got "slightly" more consistent at it today, I can definitely see how a pro can do it all day long.
I was on a 9' GC today with double shimmed pockets.