That's the problem with aftermarket stuff, a lot of it fails to actually be an improvement on the OEM stuff. Not to mention the engineering really is not there.

There are two levers in the parking brake system, one at the foot pedal, the other at the caliper. If you lengthen the lever at the pedal you will get more travel of the lever at eh caliper, assuming you are not already maxing out the travel there, this might help.

Here's a link to a Mustang rear caliper that might help you figure out what it's supposed to do.

http://forums.corral.net/forums/general-...king-brake.html

You'll notice that as you use the parking brake it tends to screw the piston out of the caliper, this is to take up slack in the system. If the piston is too far in, like on new or rebuilt calipers, you may have to unscrew the piston out some, or work the parking brake setup till the slack is out, then the parking brake will hold.