Hi Hein,
The main decision for you to take is: Will you let the tree grow another main stem, and grow more bulk, or are you happy with the trunk for now.
If you decide to grow a bit more trunk & you want to reduc the top scar a little, I would remove all but one branch for each bud to start with. Then I would remove all growing tips from leftover branches. Except for the one branch you want to become the new leader. [choose the one strong shoot almost at the cut-mark) This will effectively send a massive amount of energy to the leader, which will grow extra-tall, and extra-thick quicky. Make sure you remove excess wood at the top: You want to bark to be able to cover the cutting-mark on the top.(To see what I mean, look at this tree:
www.bonsaiempire.com/media/kunena/attach...s/667/bonsaibase.jpg; There I have cut the top some 2 years ago, and after taking the side-branches to keep, removed most of the wood. That allowed park to form, and the cut is now reduced to 1/3 of the original scar, the rest is grown over by bark).
Note that all branches that you leave on while growing the stem might be sacrificed at some point. They are mainly left on to create taper, but will most likely become too heavy to be used in the final tree. Another way to create taper would be to remove most of the branches, and let 2 sit on the stem itself, one at 1/3 and one at 2/3 of the current trunk; These will be sacrificed when you have the trunk you want, but for the comming year you let these grow as tall as you ant. Ideally these sit on the back of the tree-to-be. And naturally, you leave the leader all the way on top grow as big as it wants too.
On the other hand, if you decide: I like the tree as it is now! I would still remove all branches that you do not need: Any bud with more than 1 branch needs to have all but one branch removed. All branches on the same level need to be reduced to 1 branch. Then you need to ensure that you are left with a balanced number of branches on either side of the tree when you look at the front. Eventually you will be left with the main branches for your tree. These I would trim back to the second node (Second leaf) so it can regrow with shorter internodal distances.