Drill The Hole!
Today I saw a car on the highway with about 5 magmount antennas on the trunk. Sadly I was driving and didn't get a photo... But I wanted to weigh in on this subject none the less. Okay so when I was young and stupid, I always thought that magmounts were the way to go. But back then the internet was not really the wealth of information on such things as it is now. My advice to anyone who wants to use a radio in their car, for any reason, is to drill the fricken hole. You will be much happier with the reception. Sure it will make a hole, but they can be filled easily with a grommet and some caulking. Even leased vehicles will usually be alright with a hole in the roof, patched with a grommet. Magmounts are not supposed to be used when the vehicle is traveling fast. Believe it or not, they will usually hold on at highway speeds. But just wait until that crosswind hits and knocks your antenna off the car scratching your paint. The magnets themselves also tend to scratch up your paint finish over a large area. Drill the hole... Toss the mag mounts... Get an NMO Mount... Do it right!