I have a good idea, I think.
These marine carbs dont normally have a bowl vent hookup to a canister, yet the automotive ones do have one. I am thinking of drilling that hole and hooking up the fuel pump vent line. If the fuel pump diaphragm fails and pumps fuel up the sight tube, it will enter the bowl vent and overflow the chamber and flood the motor out similar to like it would with the vent tube entering the flame arrestor. Point is I dont want to drill the flame arrestor and it seems a neater install.