It is a bad idea to keep it on the dash and a worse idea to move to the dash during a traffic stop.
Interesting that you say that. Do you have a reason why?
Not trying to be argumentative, but a friend of mine is a Mesa police officer and suggested the dash as a good place to set a holstered & loaded weapon (with hands on steering wheel) in the event of a traffic stop. His premise was that it was in plain sight for the officer to see, as well as your hands.
I've since then gotten my permit and it's been a few years since this conversation with him, but it sounded like good advice at the time.