I used the two line locks, for the front I had a rectifier out of an alternator so as not to energize the back brakes. Worked great with two step and delay box at 3000. Later on when trans brakes came out I switched. Also tried the throttle air bottle gizmo, it let the pedal go to floor then delay box on release activated the air plunger to snap the throttle on. I liked that system better because the squirters were not used up.
I built a system like you describe, did not use a rectifier, or a delay box. Just locked front and back brakes, my Dodge had drums on all wheels then. Stage the car, hit the button lock the wheels, air cylinder expanded and held at launch RPM, released the button, line locks released, air cylinder closed and launched the car. You could dial it into the tree by changing the air pressure coming out of the bottle with a regulator. Worked very well.
