Deacons Kenya are in the same predicament. They manage their exposure to ZAR by hedging...(w/Barclays, I believe).
Depending on the gross amounts you deal in, this may be an option for you too i.e. a forward contract to exchange your future cash-flows at a certain/known price/rate.
The variable factors include but are not limited to the (1) Spot rate at the time of entering the hedge and (2) Interest rate differential (S.A vs Kenya) that will be used to derive forward points...you can keep an eye on these two factors and make your decisions on when to hedge accordingly...
I believe you are familiar with the concept as indicated on the KNAL thread..
the deal wrote: KQ can live with oil price´s above 100 U$ as long as they´re stable just like now because of hedges...what they cant live with are oil price swings i.e 140 then 35 like in 2008 cos they will have hedged somewhere at 70 and if fuel is at 35 at that time it means they will be making losses however this is a thing of the past too since KQ has adopted revolving hedges i.e they hedge for a short period of time.
Over time, you should achieve a "smoother" rate...