Not easy to see where exactly I drilled the holes but hopefully this helps and gives you an idea
The last photo just has some green dots roughly where I drilled my holes, I used a two inch drill piece, and made 4 holes in total, two directly in front of the filter head, if you were to put your chin on the filter and look straight forwards I did the two holes there, and then two as close as possible as I could alone the underside of the scuttle panel, none of them can be seen from the outside of the car, or in the engine bay unless you get right in and look