I've taken a torch, heated the ends of the slots, and hammered them to 3/8 of an inch with a bolt laying on its side at the end of the slot. Little bit of grinding here and there. I believe I got it to around 32 all in and let it fall around 16 at idle. I doubt 9:1 would give issues.
It's in a Mopar action article called "snap, crackle, and pop".
I was about 23 years old back in the late 90's. Thats when I learned how important it was. I swear the power was up by 20 percent.
Does four seconds flat still sell that book and those plates in a combo? That would help him a lot.