Can't beat a ss whip for an offroad vehicle. Fiberglass whips wont last. If you trail ride, with lots of low tree limbs and such, I wouldn't mount it top of the cab unless you re-enforce your roof and mount. A large low limb will pull your mount right through the thin sheet metal.
On my old mud trucks,I used to
mount whips on the front bed rail, right behind the cab on a large spring. Used a piece of angle, 3-4", and bolted it through the bedside and the top rail and mounted the whip there. Never
budged. We'd run some pretty tight trails though. Lol
I've mounted them on the rear bumper too, but front of the bed seemed to work best.