Most of the PL259 mounts as well the A.S. "clip in" mount are not very strong. If you hit garage door frame or underground parking ledge, you might lose and antenna.
The strongest mount is the NMO (New Motorola). It does require a 3/4" hole and the best place is in the center of the roof.
Trunk lip mounts and mag mounts do mar the surface they are on and can be more destructive than a permanent mount even considering the hole.
The NMO270 Larsen is one of the best dual banders money can buy and some what sturdier than the Diamonds.
Alan, KØBG
www.k0bg.com