The Matrix XRS models are 11.5:1 stock, they boost them to 9psi with a Water Injection setup.
I'm not the expert on this particular subject, but that's a different engine all together, and a different tuning system, correct?
However, water-injection helps alot..or so I've heard. I understand the chemistry behind the setup, and I think you meant water-methanol injection, which can actually cool the charged air down (water) and add loads of octane (methanol), all of which brings increased safety and more power at the same time.
If I were in the situation you were in, and I HAD to boost that high-compression motor, I'd use water-meth injection as well as a good intercooler.
Forged pistons, although stronger, are not necessarily going to work the greatest in your application. Those pistons are more than likely designed for all-motor, which means the crown on the pistons are not "turbo tuff", or thicker than your average piston. There's a reason why turbo pistons are much heavier than all-motor pistons. Keep this in mind when tuning the boost.
I've always been told by many, many mechanics and engine builders the same thing over and over: "It's not about the physical boundaries of modifications, it's about how much money you put in, how good the tuner is on hand, and how hard you drive that setup after it's completed."