[Donut]

Have your 3rd robot start with a ball in its intake lined up directly with the boulder the 2 Ball opponent would grab. Reverse intake at high speed, hitting the ball on the center line and hopefully knocking it out of position enough that the 2 Ball robot fails to acquire either ball. Alternatively if the ball does not move far you have now placed two balls very close together and the autonomous 2 Ball robot runs the risk of possessing two balls simultaneously while trying to acquire the center ball. If this occurs the 2 Ball robot will incur both a G38 and G41 foul for crossing the defense with 2 boulders, at worst cancelling out the extra goal with the 10 point plus tower strength increase penalties (this assumes the robot somehow scores despite 2 balls in an intake not designed for it).

You run no risk of penalties for crossing the midline or contact with this strategy. You sacrifice scoring a ball yourself, but for a low goal or defensive third pick defending a 10 point goal is a net positive versus 5 or no points yourself.