Because the centre line of the tank should be level with the centre of the carb then any tank will tend to syphon when it's filled. The best practise is to only fill the tank immediately before you're ready to fly. As you've found, it's impossible to flood an inverted engine from syphoning because it just dribbles out onto the ground. Fuel will syphon faster from an air bleed carb like yours because it doesn't have the second needle to give more restriction.