OK - that being said, there are mould making firms that can make you anything you want, in a slug.

I would think something in a 500gr. or 600gr. might be just fine in that twist - much lighter than the typical 900gr. for a .600 nitro, but still much 'better' than a round ball.

You want to be able to get enough speed out of it, to make the whole 'lesson' worth while. I'd think 1,450fps to 1,500fps would do that.