Mag on the roof should be fine.
The thing to remember is, have the sheet metal between you and the ant.
I am not saying that your head will burn up either, but long term exposure to this crap this close, at these levels is a big no no.
We get plenty of it from the towers that are installed everywhere. There is no need to rad yourself any more. 3 watts that close would be... "bad"
If you are not drilled through your roof and grounded solidly to the sheet metal of the vehicle, you are not seeing your best gain. Ask any ham radio guy.
For me, getting rid of my glass mount, then my mag mount and going to a drill through was night and day different. When I got rid of the vehicle, I just left the 50. 00 ant in there.
By the way, I warned people about being careful, but I did not thank you for posting this.
Thanks for the original post!!! I know someone who is already drilled through roof who lives in a very rural area and could use this thing
Thanks again!