Thunderhead is a really POOR choice as a bonsai subject. The main problem is the thickness of the new shoots! They are as thick a pencil, at least!
Wait!, you say. Don’t we want thick trunks?
Trunks, yes. But not the twigs. Once the tree gets somewhat ratified, we want slender twigs to make nice pads. Thunderhead makes huge twigs.
Stay away.
Mikawa is an island of Japan. It’s said the JBP from there make good bark, and the needles are a little shorter.
The cork bark pines are grown for the cork bark. They rarely make nice classical bonsai. Difficult to wire as the cork pops off easily. They’re weaker than standard JBP.
KOTOBUKI is a sport that has naturally shorter needles. It often makes an extremely large number of new shoots coming from one spot, which need thinnng out. It’s popular with those who don’t know how to decandle properly to get short needles.
Good JBP have Good bark, dark green, straight needles, respond well to decandling, and have short internodes. The best way to get good nebari and get nice low branches is to use the Seedling cutting techniques as described in Bonsai Today magazine Issue #20. It’s teprinted in the Masters Series “Pines”.