Very nicely styled trees. I have 2 of these right now similiar in size to yours. Havent styled them yet though, just been sorting out what I want to do. But seeing as many shimpaku as possible seems to help a bit.
Very nice and healthy shimpaku, and Vev has some good suggestions.
As you can see, Vev suggests to create jin from the lower branches, and then you need to bring down (severely bend downward) the higher branches. This will create a much older-looking tree.
This kind of design is for the more experienced bonsaists, I hope you already have that kind of experience. If not, then you should seek help of an experienced teacher who understands the design suggested.
It will look great if done properly, but if executed poorly, it will actually make the tree look worse than now. The key points are: bring the upper branches down and close to the trunk, keep the foliage pads compact and short, keep the negative spaces and foliage pads well defined, but paying great attention not to create the pom-pom look, and paying attention to the effect created by the horizontal lines of the pads and slanting lines of the branches.
As you notice on Vev's drawings, the bottom side of pads are either entirely horizontal, or start off slanting downwards and then they turn horizontal towards the end.
This is the problem with your trees right now: some of the pads have no horizontal lines at all, but they just slant downward all the way. This is an absolute no-no. Lack of horizontal lines creates the impression of somewhat sloppy and unfinished look, and lack of balance. In order to achieve balance and maturity, the bottom part of pads must have at least one horizontal line (they can start off slanting, but they eventually have to turn horizontal). This is very easy to correct, but I've seen many times that people overlook this small but vital detail, and can't figure out what is missing. (BTW, when Walter Pall says that "every little branch is wired", it is because of details like the above, must be paid attention to).
(The exception from this is when you try to achieve a "weeping" effect with some spruces, firs, and cedars, but this is never the case with junipers and pines.)
Any more photos of the twin trunk. I especially like what Vev suggests for this tree. The only question I have is : in the first set of photos the twin trunk seems to have two apex branches. Is this an optical illusion ?
Mmmmm, depth of field..... Nice photo. The trees have advanced nicely, appearing to have aged considerably due to foliage work. I'm sure a few more years and the pads will look very full and well defined.