What throttle/brake servo are you using? If it's the Hitec 645mg, I don't think they have enough torque to pull the stock rear disk.. Therefore it will take forever to stop the truck.. Switching over to a higher torque servo will work better.
If you plan to run front and rear cable brakes you will need one hell of a servo.. The Hitec 7955 is a good start, it has 333oz of torque at 6.0 volts and is almost twice as fast at .15 transit speed.
Trip..
Hey Trip, i have a 645mg on my rear lay shaft disc brake, and it was rubish, untill i installed a carbon radio tray, to stop flex, and now it is great, still not as good as Hydros...