I'm not familiar with the Predator stock, but there's another guy making adjustable combs, a fellow named Karsten. His comb was featured in an
article at Sniper Central and I see that Savage is using his comb on the Long Range Hunter series of rifles.
From what I'm able to understand, it's fully adjustable, is installed with a hand drill, and is recommended highly.
The guy doesn't have a website, but the article gives an email address. I'm thinking about ordering a couple and giving them a try.