Would the dome light area be a decent place for one? I've truly never given it any thought before, or even noticed them much. And I guess 99+ percent times I've even seen them used was on the TV news or bad boy shows. It seems to my recollections a large number of those were actually mounted either above or behind the front seat.
One thing I do know without a thought is that I want nothing to block in any way my vision while driving, right, left, center, high or low! It's difficult enough avoiding distractions no matter how hard you'll try, so why add to em.
Graduated HS at 18 and hung the tassel on the mirror of my 64 Impala where it stayed for less than a day, and nothing that I can recall has ever hung there since and that's going on 50 years now