I'll try to take a stab at a virtual for the deign I discussed earlier, but it might be a while as I am pretty busy with work and family these days. No matter which design you go with, reducing the thicker portions of the upper branches in favor of natural movement and ramification could help the design down the road, or could get chopped off if you decide to chop it.
Those are some nice roots down there. I have been real conservative with the roots on my hemlock, just because it is my only yamadori, but it has given every indication of having strong roots that take well to reduction. In general you will need to ground layer in order to bring the roots in. You can do this a couple ways. One is more passive and less guaranteed but less risky, which is to plant it deeper, which it looks like you have already and hope that some roots sprout further in and the outer roots can be reduced. Or more actively, you can remove or damage the bark around the roots where you want new roots to sprout, apply rooting hormone and some spagnum moss, and recover with some soil. Since there is not a lot of institutional knowledge with hemlock, and how it responds, you may want to stick with the first method, reducing thicker outer roots a few at a time duiring repotting, but also experimenting on some of the outer roots with hormone and bark removal, to see how it responds.
