I couldn't use a mag mount if I wanted to. It's a mustang convertible with trunk and hood made of fiberglass. Magnet no stickee.
The only place I can put a mag mount is on the fender next to the trunk. I tried that for a little while, but the fender is slightly rounded, so the magnet did not have a completely flat surface and held even less firmly than usual. It didn't fall off, but it had a tendency to walk off the fender and would have fallen off in a short time if I hadn't moved it back several times.
I still didn't want to drill visible holes, so I got a lip mount. It is screwed in place, but the screws are on the inside, out of sight.