my guess is you need a min. of 3 to get the ball "trapped" in there for any period of time
with 1-2 two - it's going to hit the pops and go right out.
I love when a ball gets in the pops and goes crazy - sort of a throwback to EM games for me when that was where all the action was
The single pop on TNA is not a whole lot different than a sling