I installed a parking brake while building. It was not real complicated and I would do it again. See pics and narrative on my kit-log starting at 9-17-12. I very seldom use the parking brake, but when you need one--you REALLY need one. Like when you're solo, pull up to a self serve pump at a remote airport and find yourself on a sloped apron!
All models are pretty much the same except the 4's and 8s are tandem. These are pictures from an RV-6 install with a T-cable on the wall.
This system only works for the pilot side anyway I think. I've never tried from right side.
On the RV-8A, the RV-10 and the RV-8 I made a simple bracket that mounts to the bottom center of the bulkhead just forward of the panel. The kit provided brake lines are long enough to reach.
The advantage doing this is simpler installation and no parking brake actuator cable. To set the brake I just reach under the panel and through the valve lever 90 degrees.