Everyone has an opinion and what works for one person may not work for the next. Any engineer should know about variables and assumptions. About the balance thing. Remember that the heat crossovers are only connecting 3&5 cylinders to 4&6 cylinders with a tiny port which is not nearly the same as having a balance tube or x crossover in the exhaust system. Besides every manufacturer used a heat crossover on their engines for heating the intake manifold. That's my thoughts. I fill my heat crossovers in my heads.
