Lip (motorized or not), mag, clamp, and other non-permanent mounts will all give less than stellar performance. Oh, you can get by with about anything including a dummy load. The best place to mount one is on the right cowl. If you just can't bare to drill a hole, then use one of the hood seam mounts made especially for the Jeep.
If you want the best dual band antenna, then that's a Larsen NMO2/70BK. Anything else is less.
There is more than just the antenna to worry about too. Look over my web site for details.
Alan, KØBG
www.k0bg.com