I think that if you dont go in the rainy season you should be ok.
I just did a trip to Botswana, and if I did'nt need to takkle the mud I would'nt even have used low range at all.
I think the terios is very capable, just be carefull and drive sensibly.
I dont think fitting a tent to the roof is a good idea as the terios is not that wide, you might be a bit top heavy, also find out what is the allowable mass that the roof can take.
Discovery 3 V8 SE
Self designed Rock and Tree Sliders.
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1981 Series 3 S R6 88" Allmost Perfectly Restored