Doom,
I think you have a good idea but I would definitely do some research before drilling. Haven't seen a lot on the SF so I couldn't say yes or no. Trust, I'm not trying to be derogatory, I'm just trying to get people to realize a.) The ball still has to be THS friendly and b.) designing that reaction for a sport pattern is going to be difficult so be sure to do the research.
I've seen a lot of people with holes in the back of the ball thinking it was Motion hole without the layout. I had a customer come in with the CG 2" from the Center grip where the driller plugged the P2 hole and then put a hole in the back. Ball rolls like crap, I get it, weigh it up, its got 2 ounces of side and 1.5 Ounces finger. Layout wasn't right to begin with, plug the whole ball, get his PAP, drill it correctly, guy goes out and shoots 700 and he's a 180 avg bowler. That is why i'm so vocal about getting you PAP, And following the steps, doing the research and drilling the hole for what you need.