Funny fred this, so far.
Me thinks it is your personal choice to have one or not. Initially, I am one of those pro-carnet persons, probably because I am in shipping. But after reading all these posts, I realize you don't need one.
This is Africa. There are also a lot of people here who have by far less money available than peeps who travel around the world for what it's worth. Yet they also do travel and cross borders. Most of them probably never heard of a Carnet.
Every single country will have some kind of formality to be done to use your means of transport. Now that can be clarified at the border. Sometimes it may take some "convincing" and will require lots of time and talking, but that is part of travelling through Africa.
My real problem would be to asses, which option is going to be cheaper, the Carnet or the tea money option?
How are you going to plead poverty to the Customs official, arriving on a R1200GSA?