I know there are naysayers out there, but I would install it in the AC breaker box, namely the (in your case) 50 amp main breaker. The breaker lugs typically have enough room to accommodate the extra wire and the neutral and ground bars are right there. Just ensure all the strands get into the lug and it is torqued to the proper spec. and then re-torqued it every 6 months to be safe as should be done anyways.
The speed that the surge travels, it does not matter if the protector is at the pedestal or a specific piece of equipment, the voltage surge will travel on the conductor until it finds a weak insulation point. That is, unless you have the proper surge protection to sacrifice itself instead of that expensive TV.
Being on the main breaker also protects you when running a generator or on the shore cable.
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