I don't feel I have enough experience with tridents to tell you one way or the other, however I did just ask some of the more experienced posters for suggestions on my trident, and they convinced me to cut back every branch all the way to the inital stump. From what I read and from their advice, tridents are quite prolific growers. When you cut a large branch, many adventitious braches will sprout from the cut mark. Leave these braches to grow and help close up the wound. Your stump appears to be somwhat small, so it might do well with some time in a growing box to help thicken up the trunk; this would probably also help it to recover from the shock of pruning. I would prune it hard to get your initial trunk line and then let it grow wild for while to thicken up the trunk. Then prune it back all the way to the trunk again to start developing nicely ramified branches (this is the step my trident is at in the link below). There are some great articles online to help you develop this tree, and also some great advice from the pros in the thread below. Hope some of this helps.
All the best,
JDL
http://forum.bonsaitalk.com/showthr...83&page=1&pp=15