This what I posted on the Jeep JL Forum this morning:
Seriously, there isn't really any ideal/optimum locations for two-way radio antennae on Jeeps. So, wherever you can mount an antenna is about the best you can do and you just have to live with the performance. Overall, it'll work fine especially for trail comms.
Some professional grade antennae like Laird and Larsen do offer non-ground plane antennae that will help with the lack of an antenna ground plane, and they are great for the side cowl mounts, but they do need to be trimmed/tuned.
I have four radios in my 23 Wrangler Rubi 2 Dr. For my CB Radio, I use a Firestik II antenna off the rear tailgate hinge. Also, I run with a VHF radio and I use a Laird non-groundplane antenna hanging off the driver's side front cowl, and two UHF radios, one analog for GMRS and other analog frequencies, and one digital UHF radio for my radio club digital radio system soon to be statewide. The digital radio antenna is mounted on the hood with a lip-mount and the GMRS analog UHF radio, I use a Glass-Mount antenna mounted on the rear glass.