So this is why i asked? Typically my JBP have a trunk diameter of 1" at 3 years growth. Because, I use the root cutting method to develop radial roots when the seedlings are three months old that diameter is not what it could be if grown as a nursery plant. I suspect your tree is much younger. Check to see how easily it bends.
If so, then there is plenty of time to wire for movement and prune back for lower branch development and eventual taper. Apply wire to the trunk this winter to create some movement and interest in the trunk. Then I would repot the tree towards spring in a grow box or colander. If you use a colander place in the ground for a couple of years. Use Bonsai soil mix for the grow box or colander. Begin fertilizing approximately 1 month after repotting and build slowly. lots of water but allow the roots to dry out between waterings. Pines like dry feet and drainage is very important. once the tree has recovered and is vigourous then i would plan the cutback process to create lower branchin, and manage the sacrifice leader and branches selected to create taper.