Pretty sure with the new bracket he made it will put enough pressure to lock them up.
I wouldn’t count on it.
I’ve only had a chance to test my prototype, which was a crude model of the production junction bracket, but it didn’t lock up the tires while moving. The production version is much more refined and will work more smoothly, but overall it provides the same force.
What it does is exert more force on the caliper with less force required at the handle, making it easier to get adequate holding pressure. But I don’t think the Mustang calipers are designed to lock up the wheels. Especially when you get into much larger wheels, which increase the lever arm.
Let’s not forget about another key aspect, brake pads. If you have junk brake pads you’ll get junk output.
I used EBC Greenstuff with good results, but switched them to try a pad with less brake dust.
The pad I chose was the Hawk HPS. They were junk in my opinion. Horrible cold stopping power, which is what the parking brake will be, and they required too much pedal force. Noticeably more than the EBC pads. My wife though she was going to run into the garage door the first time she moved the car in the driveway.
When I get the 4Runner back together it will be running EBC Yellowstuff to see how they work.