Ideal compression for flywheel?

[Dripto]

Hey guys, I'm currently designing a flywheel shooter, and was wondering if there were any guidelines to how much compression to aim for. Increasing compression increases both the normal force of the ball, and the deformation, which leads to more contact area, however it also relies more on the inconsistent compression of the balls, so I would like to not have excessive amounts.

At the moment I am aiming for about 1.5" to 2" of compression on the ball, do you think this would be acceptable?

The ball will be in contact with the rollers for about 12.5" of travel. (Approximate Center of Mass travel)

Thanks for your help!