Quoted from Grizlyrig:
You can try a step down converter like this.
Or you could use a adjustable motor controller like this.
amazon.com link »
I'm sure others here have some more ideas to slow the motor down. I am against the idea of cutting the weights due to it's a balanced assembly. You would have to weigh each weight on a postal scale to get it right or run the risk of burning up the motor bearings prematurely. Hope this gets some ideas in your head for you to play with.
Don’t think you can use these in spike games.