A while back, someone (pretty sure is was pauly3; but forgive if no) mentioned driptips sticking down inside atty. While I was reviewing the final drawings and specs on the atty, I was reminded of something. I had originally/always drawn all versions of the Nuppin' with a 5mm thickness on the top of the cap. This was the # that I got from measuring a bunch of driptip stems. I had made another decision afterward (and without recalling, came to the same conclusion again on this vers.): I want the outside (perceived) line of "cap thickness" to be lower than the actual ceiling inside. This because I want anyone to be confident, when judging their coil height, that if the
coils are no higher than the line (outside) btwn AFC and cap top, there will be no issue with clearance at the ceiling. So, then the driptip protrudes a bit on the inside. Usually, however (on average for many driptips), no more than the "imagined ceiling" based on above trickery. (←that is not a promise. driptips vary)
Like when you're sizing up your coil height like this . .. .
and you want to know for sure it's not going to touch the ceiling . .. . so you use the line of AFC top as gauge and know for sure you've got a little clearance to spare.