MAKE SURE if you do a rear "up and down" and the opening low as pictured above, that you TEST it for SIPHON. Determine the low side if any, fill it close "to the top" of the filler and then park it "vent low" and see if it siphons on a hot day.
The beauty of the 69/ earlier vents is that they were vented way up high in the filler, which formed a "siphon break." The only way they would siphon (a little) is if they were filled up (or heat expanded up) into the neck, above the vent connection. Then they would only siphon ?? a quart, whatever ?? until the level got below the vent line in the filler, and "break" the siphon.