Specifically, I see many RVs that add three or more panels.
RVIA and QAI (Canada) specify following the National Electric Code (NEC - NFPA 70) in all RVs. Most RV insurance companies require owners to comply with standards and industry best practice on modifications that may effect safety.
The 2017 National Electric Code (and 2020,2023 editions) have this requirement: "§690.41.(B). Ground-fault protection. PV DC circuits that exceed 30V or 8 amperes shall be provided with dc ground fault detection meeting the requirements of 690.41(B)(1) and (B)(2) to reduce fire hazards.
Solidly grounded PV source circuits with not more than two modules in parallel and not on or in buildings shall be permitted without ground fault protection."
My Escape Trailer Industries optional OEM configuration has two modules in parallel (GoPower BF-190M). The charge controller (GoPower or Victron) provides grounding between the - PV terminal, - battery, and chassis. This meets the RVIA and QAI requirements.
I placed a 30A MaxiFuse and a disconnect switch before the charge controller. I have a 60A MaxiFuse between the + solar charger and the + main bus.
73/gus