These bodies are made from closed cell foam.
This is a “high tech” material stronger and lighter than balsa.
This foam can be glued and painted with all the same materials as balsa including cellulose.
Foam will never take on water. Glue a 1mm glass or carbon stem through the body with about 1cm of stem above the body.
Then glue a 1.5mm or 2mm hollow tip on to this piece of stem.
Use 1.5 or 2.0mm tips with a 1mm bore.
pack of 8