Fair enough. Maybe a well placed disguised rock at sump height could be stepped over by nags but catch out the petrol heads?
Cant remember where I seen it but the was a steel barrier about 1.5 feet high so that a horse could step over but to high for a car. I guess the 4x4 people could see it as a challenge though
brings back memories of pushing elephants back though the fence in the dark up near nanjuki/Timau.