on my N33 (hull nr 787), the vent is on port, on the side of the hull (actually there are two holes, may be one is the tank vent and the other one the vent for black water, I did not check). When I hear a noise of bubbles coming out of the tank vent I stop filling. As the red cap doesn’t fit perfectly (the former owner mishandled it I guess), I never fill the tank completely (not more than 75%), otherwise water leaks into the bilge when the boat heels seriously.
The filling hole is on the deck, on port, around 2 meters from the bow.
I’ll de back on my boat next sunday and will be able to make additional check if you need.