Sometimes Bumpers & Kickers don't mix

[MrForbes]

6.3.1 BALLS

While playing Breakaway, ROBOTS manipulate BALLS to accomplish the objectives of the game. Each BALL is a standard Size 5 soccer ball. The BALL weighs between 14 and 16 ounces, has a circumference of 27 to 28 inches, and is inflated to a standard pressure of approximately 9psi.

let's see....28" / 2 pi = 4.45" so the spec ball radius could be pretty close to 4.5"

at least to within the accuracy that you can measure the position of the lower front corner of the bumper!