Im 6-3, I dont think size is factor. I did get stopped once with my ar-15 sitting in a gun case in the passenger sit. I was out of the car when I was stopped. I just got home, cops were driving by following me cuz I had a broke window. They were looking at me, I stared at them, thought I might know them or something, dad was a cop. But I didnt, so as Im getting stuff out they backed up and asked for id, insurance etc. So I told them insurance is in the glove compartment, and there is a gun there in the seat, so I made them get it. They just thanked me, very nicely, one asked what it was, and then said they are really nice guns and likes them.
I thinks its all about attitude.
and Ill say it, Im white I think that makes a big difference too. I dress "normal" not like a thug or gang banger, no tats, so Im sure that has something to do with it.
You're absolutely right about attitude, but I do disagree with the size not having a partial affect, this being part of their personal comfort level. I'm 6'6" btw. I work closely with law enforcement, and its pretty easy to see the difference between cops who are confident in their ability to handle potentially volatile or dangerous situations, and those who are not.