The underparts pattern fits Pale best: the chest is well streaked and the belly rather uniform (kind of the opposite in DCG: breast usually plainer and belly neatly barred). I also find that in Southern Africa, the rusty coloured underparts of juv/imm Pale is a good indication, juv/imm Dark tend to be darker brown.
The clincher is the undertail pattern: the black bars are broad and well defined, a DCG would show thinner and less distinct bars. Also, the underwing markings strongly points towards PCG, especially the secondaries: the blacks bars contrast sharply against the feathers (on DCG, this pattern is only subdued) and they show a broad black trailing edge. The underwing coverts of juv DCG are delicately and thinely barred, here you can barely make out a pattern.
Lastly, in Namibia, Dark Chanting Goshawk occurs only in the extreme North-East of the country, towards the Caprivi Strip.