You can probably (I haven't verified this) omit separate radiators and just use the back of the solar panels. Effectively you're describing mounting each H200 to the back of a 4 m^2 solar array at which point I suspect the equilibrium temperature will fall within an acceptable range. In fact the H200 and electricity are both entirely irrelevant here - the core question is what the equilibrium temperature of a black planar surface is at a given distance from the sun.
Would it be feasible to put several JWST-like stirling engines somewhere in the mix to use up some of that heat and turn it into some kind of useful energy? ....
Perhaps running pumps that move around coolant passing over the cubes of GPUs? ..
That would be extra weight/cost into orbit though...
Also, don't solar panels have reduced efficiency when they're hot? And having anything hot surely increases failure rates.. with metals getting closer to melting points...?
We should be well below the boiling point of water here, not anywhere near the melting point of metal. Any panel efficiency gain needs to be balanced against the energy required to cool the panels, the added mechanical complexity, the added material expense, and the added weight to orbit.
Ideally this is a static structure with an equilibrium temperature acceptable for the silicone to operate. If the required panel area is too hot on its own then a perpendicular cooling fin on the back that falls entirely within the shadow is added.