Holger, I can't tell from your post whether you have actually been to Angola or Cameroon before? Operating commercially in those areas is difficult enough, to try to fly around in them privately would be an open invitation to all the corrupt uniforms to shake you down for every last one of your dollars. That's before you get airborne. Should you have the misfortune of getting airborne in your light piston you'd have to deal with downright dangerous ATC, the motley collection of eastern-bloc rustbuckets hurtling around without reporting where they are, zero search-and-rescue, the list goes on. Read the 'You know you're in Africa when..' -thread.
Sorry to be so negative, but CavortingCheetah is entirely right, unfortunately.