I don't even know what that diagram is supposed to be doing. Why do you need or want a second solenoid "What does it do?" Why do you need or want two large gauge wires going from front to rear?
The 8ga wire carries the load while the car is running and is connected direct to the alternator through the existing wiring beyond the amp gauge. The solenoid in the trunk is used to send power through the other large wire (1/0ga) only when the starter circuit is energized to power the solenoid. By running a jumper to the starter mounted solenoid, I avoid having to put in a different starter.
By running the 8ga wire to the amp gauge, there is no battery juice under the hood other than the alternator stud. And the only way to engage the starter is to power the solenoid in the trunk, so there is no way to jumper the starter.
And by introducing a security interlock, there is no easy way to power that solenoid without the proper switch being set.
So, in theory, there is no power available under the hood that could be used to turn the motor over, even if the ignition circuit was jumpered from the alternator stud (the only point of power left).