Clenching clay pipes was not for the timid man! That makes my teeth hurt.I was out at the Smithsonian natural history museum and saw some interesting pipe clenching evidence from early American Colonists. Several skulls had round holes in the teeth indicative of clenching a pipe.
http://anthropology.si.edu/writteninbone/pipe.html
This skull was from a 25-29 year old man.
I prefer lightweight bent pipes for clenching. I can't stand softie bits, I feel like I have to bite down harder to keep the pipe from waggling around if I turn my head.