First thing, you're all over the map, and incomprehensible. You make mention of a ball, the Cruel c51, but then you just go haywire.
Are you wanting to construct an entire arsenal of Motiv stuff, or would it be alright to mix in stuff from other companies? Do you want the Cruel c51 to be the strongest ball you throw, or just somewhere in the middle?
And, the Slingshot is NOT PK-18, it is PK-17, which is milder.
Be a little more specific, and narrow down what you are talking about, and I'm sure somebody will be glad to help.