Yes, taboo for the most part, I understand that pinions of low numbers of teeth are sometimes enlarged to reduce undercutting of the teeth, which would be less of a problem with 20 degree teeth than 14 1/2 PA. I saw mention of it on Machinery's handbook once upon a time, but know less than a little about it. having the center distance larger than it is supposed to be makes for noisy operation and high wear.