Maybe what needs to follow is the cap.
Look at the battery end of a kr808d1 carto, if we could drill 2 small holes on the edge, and make the center one just slightly bigger, it could then replace the inner cap all together. No more glue, no more nothing, these metal caps could be crimped in place.
Underneath the caps they caould have a small, oval shaped, silicone o-ring, a thin one, basically just a factory spacer-washer.
Then you have your regular mouthpiece cap, or you could even use a 901 whistle on the 510 cartos, I just found out it fits it well if someone wants them they can use them.
For the future, the whistle could be designed to allow the airflow in the center, with filler around it holding the flavoring, menthol, ry04 enhancers, berries, whatever.
what do you all think?