More than one modern instrument has suffered structural damage from overtightening the head. The next time you go to a bluegrass festival, take a look at how many banjos have resonator flanges that have been bent out of shape by excessive head tension. The older skin heads had a safety feature built into them. If you overtightened them, they would break. Mylar doesn't do that.
Many people have different theories as to the correct tension of the head of a banjo.
Mine was developed by experimentation. In 1971, John Ike Walton, drummer and banjo player for the 13th Floor Elevators, stayed with me for a couple of months. He had a Fender Artist's Model banjo, which was very similar in construction to a Gibson Mastertone. As we discussed the setup of the instruments, John started thinking out loud. You know, it is possible to tighten a drum head so much that it chokes off the sound.