Vaal to Durban offroad in December - help needed with route

[tifua]

Brother and I looking to do a ride from Vaal to Durban (as much off-road as possible). I have a basic route that will get me as far as Harrismith using railway service roads and farm roads however any suggestions or alternatives would be great for Harrismith to the coast either north or South of Durban is fine. If you have more technical routes / GPS tracks / old legendary routes through goats passes - something bit more exciting than ordinary railway service roads please let me know. Trip will be on XR650L and XR650R - both are roadworthy but would prefer to avoid tar or main roads much as possible

thanks -