I think sooner rather than later for getting the heights correct on the smaller trunks. The second and third largest trunks should be about 2/3rds the height of the main trunk. The smaller diameter trunks should be about 1/3rd the height of the main trunk. If you can, avoid exactly half. The "rule of thirds" keeps the eye moving through an image, if you make one exactly half, the eye will settle at that point as a static point. Of coarse the "rule of thirds" is a design principle, which is really just a suggestion. The design principles are known to work, ask anyone in print advertising. But you don't necessarily need to follow them.
You could reduce this to a single trunk, but for the moment, I think the 5 or 6 trunk clump is interesting. If the roots allow at the next repot, you could separate the main trunk, and keep the remaining clump of 4 or 5, as a separate clump bonsai. You have good enough variation in trunk diameters that the separation could work.