Here is a drawing of what my darts back in the day looked like.
The dart shaft was wrapped with cotton about 3/4" from the top of the shaft so it was always centered in the cone. The cone bottom was supper glued and twisted as inserted in the cone. The shaft would stop when the super glued cotton wrapped shaft hit the bottom of the cone. I then would add a small amount more of SG or ? to soak into the rest of the cotton, and a bit around the cotton on the sides for added cone strength. The cotton inside structure was extremely light but exceedingly strong so I very rarely had any cone collapses on hard contact.
This is the only legal cone we are allowed to have in California .... A picture of one !