Quoted from YeOldPinPlayer:
That is impossible. You changed the width of the tunnel shot from x to x minus (the increased radius of the new rubber).
theoretically impossible but in practice if x is 10 and the increased radius is .1 ( 10-.1 = 9.9) when you round out the answer which is fine for pinball (but not good for quantum physics) you still end up at 10- good enough!
the bigger effect is that extra .1 radius has an significant effect on the angle the ball EXITS the lower post area so when you factor in the remaining distance to the flippers the thicker rubber has a large effect on where the ball ends up.
the tunnel shot is just hard to dial in as you can not see the ball as it gets near the orbit entrance. I have the thicker post and it helps the exit and the difficulty of the tunnel shot seems about the same, everyone once in a while I will get some weird ball bounces from just below the last pop that sends the ball flying down the left outlane but the thicker post has nothing to do with that jusr random "that's pinball" irritations