I have done the border track a few times, always found it easy. Some people have trouble with the sand dunes but I have always been able to idle up them, low tyre pressure is the key. I think I had around 12psi.
Be careful with the bog holes at the end, some can be over roof level when full of water. Test with a stick if unsure, the deep ones can be avoided.
I have had no problems with the Harrop locker. I hope it holds up because I like how it briefly unlocks when changing direction, makes adjusting the line much easier with no power steering.
I pulled it out on the weekend since I am rebuilding the whole axle. Has some rust on it but is working fine.