Mike, some more thoughts: The issue in the Kaokoveld is filling stations. The only reliable are Opuwo, Ruacana, Palmwag and Kamanjab. You might get from jerry cans in Purros. Sesfontein lodge has a pump. But both are not reliable. I am not aware of the situation in Epupa, Okangwati and Orupembe, but there might be nothing. From Ruacana to Palmwag is around 750 km, via Khowarib Trail to Kamanjab around 800 km. Without possible detours, if you want to drive parts of e.g. the Hoanib. All is heavy going. But with long range tanks and 2 spare jerry cans it should nevertheless be ok.
The Kaokoveld had the first good rains in many, many years. Palmwag the first rain after 6 years. You will be lucky to see a transformed landscape. But many roads and tracks are badly damaged, including the D3700. Hopefully until July the D-roads are redone. But other tracks might still be bad.
Manfred