Hello @ShallowAl . Interesting question 
Cascading RCDs requires at least the right RCD types in terms of current and trigger delay. In the diagram attached (sorry for the german text, source ABB), you see a main RCD (in your words, the upstream RCD) and a cascaded RCD. The two curves and its areas should never interfere to avoid a double release. That’s the general part of the story from my point of view. Main RCDs as first ones in the cascade are “S” types (selective).
It would be interesting, if Victron has a specific recommendation regarding RCDs between grid and the inverter for specific reasons 
In my own system, there is no RCD between grid and inverter, but separate RCDs on AC load side of the inverter. For parallel loads, I have additional RCDs for my Wallbox and the bigger loads in the house.
