Gas cap - upper wing tank

[Beej]

Hey, guys. Several years back, I got a gas cap, unvented. I refabricated it to look like a tear drop shape. Now I am painting this upper wing, I need to vent the cap. I am assuming I need to drill a hole in the cap, where, and what size dia? Does the cap need a snorkel type deal, or will a simple hole provide positive pressure to avoid syphoning?

ACSS sell the vented cap, but no picture....
https://www.aircraftspruce.com/catalog/appages/fuelFlange2.php

 

[race38]

 

[Beej]

 

[David J.]

 

[planebuilder]

 

[NDTOO]

 

[Ralsmark]

 

[starduster II]

 

[Vic Zubot]

 

[Vic Zubot]

 

[Beej]

 

[armstrong8933]

 

[Beej]

 

[mbberger]

 

[starduster II]

 

[asport22]

 

[Vic Zubot]

 

[Beej]