Yes, but there's no plug in the vent when you are flying, right? That was what my 'test' was about with turning my plane through various attitudes by hand...to see if it is going to vent gas when flying, not to see if it will it drip during storage.

I, too, plug my vent lines when not in use...and the plugs have a red "REMOVE BEFORE FLIGHT" flag attached, as well.