I’ve not got one on ours yet, we too rarely go off the blacktop.
However, that being said, I can see they’re worth the $$$. We took a trip down to Wyangala Dam a couple of years ago with our last van. Came across a herd of sheep on the road as we were leaving. Only traveling at about 20-30 km/hr on the approach to them and as we left (slower whilst in the middle of the heard!!). We all thought it was hilarious! Until I got home to was the van... front of it had sheep dung everywhere!! I never could get it all off the vinyl... it stained it quite a lot. If I had a guard the damage would have been a lot less....
For some aerodynamic quirk, Big Mal has no need of a stone guard at all, could be the tray back set up on the Colorado but I get hits on the pole tube across the draw bar, chips on the draw bar but nothing higher up and the alloy shed on the Ute would show up any richocet hits, done my share of dirt and fresh tar and luckily nothing, have no idea why......................I do know those rock tamer mud flaps if not set correctly will cause a hail storm of rocks to fly up if they hit the ground on dips and not very nice outcome.
Have found the crap from road works to etch my nice alloy wheels and stainless steel checka plate on side of rig, still haven't got it to come good.,