Your elaborate setup still exceeds manufacturers recomendations thus puts you at risk for shorts and burns.the odds of your probe reading the highest point at 104 is very unlikely. I am betting at 104, you have hot spots well over 120 degrees.
If the main (ie: the cheaper) thermostat fails in off position, your rack goes cold.
I can accomplish the exact same thing for $35.
You spent well over $100 to gain nothing.
I am really not understanding why people need to make this so difficult/expensive?