Are you running with an established group? What are they using?
Are you just wanting trail/convoy comms? Or "reach out and touch someone" comms?
There are still people/groups that run CB, while some are making the switch to GMRS. Even Jeep Jamboree has moved to GMRS, it is far better than CB...
I use one during the local VHF contest where I operate as a roving station. Furthest station that was participating was just over 40 miles and I didn't have a problem working him on 5 watts.
(old picture, old Jeep)
I made one, it was pretty easy and the pin outs are the same for the 2900. But by the sound of it, the Mobilinkd isn't what you are looking for.
As noted it doesn't function as a dumb tracker, only as a more fully featured APRS set up with display and messaging and such, really more along the...
I use a Mobilinkd TNC connected to a Yaesu FTM-3100. I liked the bluetooth between the TNC and the tablet so I didn't have to run any more cables around/through the dash.
An oddly shaped ground plane can distort the signal as it is pulled in the direction with the most metal.
With the roll bar being tied to the rest of the body it may not effect it too much, I also wouldn't worry about it too much.
Also with the soft top, if the antenna fit with the top up it...
Can you get inside the roll bar to run the coax and secure the NMO mount?
Here is another option for a 1/2 wave antenna (no ground plane): https://www.amazon.com/gp/product/B00IDTJ2KE/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
A front fender mount would work well also...
I imagine having access to the Colorado Connection (linked repeater system for those not aware) has a bit to do with the adoption of ham radio in your area?
As dreadlocks mentioned, the radio service used by groups/clubs does seem to be regional.