Yes it matters and if that vent is upside down it will not fill properly. Get over being able to see the tank as it fills you will know when its full when the fuel squirts out the vent line removed from the muffler. If that bothers you then slip on a small catch tank on the line from the vent.

Turning and airplane upside down to fuel just makes no sense. Install the tank properly as intended or you are just asking for running problems.

John