Header extensions / torque tubes?

Dave!! I have always lived by the old school way of learning how to make them the proper length.
I used 3 1/2" x 18" "Collectors/torque tubes" whatever term is used.....
I used a low temp paint and put a single coat on, took 5-6 runs and wherever the paint is burnt off to, cut them off - Mine ended up about 16", then had them jet-hot ceramic coated.
Supposedly this is where the exhaust is coming out at its peak temp/flow.
My dad did this back in the 60's on his S/S cars, I assume it still works? Maybe someone can chime in and update this old way or "fine tune it" - pun intended!