... Good point Wille. To help with that I bevel my slots on both sides, then place the carto into a drill and use emory cloth to smooth down any rough edges.
Also, I really like the triple punched cartos also. I will need to pick some more of those up. They works great with juices up to a 40/60 blend, and did OK with very high vg liquids as well.
Sounds like wayyyyyyyy to much trouble.

It also seems like getting consistent results will be tough.
I always find PG to VG ratios don't tell us much, as it doesn't take into account flavorings for one, and I doubt that every VG out there has the same viscosity. Alcohol, PG and water are common carriers, how much flavoring has been added? 2, 5, 10, 15, 20%? If the stuff is too thick as little as 3 drops of water per tankful will change the viscosity.
I've basically gone to single coil, 2Ω Boge and
smok cartos. They both seem much more tolerant of hole/slot size. I have also decided that the shorter ones perform better over the long haul when tanked than their XL brothers. I've also found that a couple top offs through my drip tip help for the first
tank, they loosen up after that.
As far as punching the finickiness of the piercing valve got old. I quickly built this after seeing a few similar designs out there.
Dougiestyle had a neat, no frills, press together approach.
Another.
Mine was precision engineered from exotic wood I found in the garage and modeled after Fono's Phideas.
The main hole (carto diameter) was drilled to the correct depth to put the punch in the right pace, the 'stop' is just 2 carto end plugs. No need to count turns, when the stop makes contact it's done.
No need to clean up anything, no need for anything except a screwdriver, and the hole is consistent, every time. It really is a 10 second job.