Actually, you could have just poked through the existing vent with a sewing needle. It would have been more accurate. The reason is these vents have a while filter adhered from the inside (like micropore tape).
You can actually see this on any transparent-bodied IEM like the KZ ZSR, ZST, ZSN, ZS10 Pro, CCA C10, etc.
Anyways, that filter restricts the air flow, effectively making the vent hole about 50% ‘smaller’. So if you poke through the white filter, you will in effect make the vent hole ‘bigger’, without actually enlarging the hole.
A very small hole is all that’s needed. For example, I make most nozzle vent holes 0.2 or 0.4mm, which makes a noticeable difference in the bass. Judging from the photo you posted, I estimate the hole you made is about 1.5mm (based on the hole’s size in comparison to an individual wire in the KZ upgrade cable).
I’m glad you liked the result of the mod; that’s all that really matters.
I cringe at the thought of all the aluminum shavings that might have fallen down inside that hole, because the dynamic driver is directly below. The metal shavings and chips will bouncing around on the fragile surface of the dynamic driver’s diaphragm. Whether or not you’ll be able to hear that remains to be seen.
When I drill the vent holes, I am able to extract all shavings and chips as I go, ensuring none end up inside. It’s taken me many tries to perfect my technique though.