Now how to get some taper........
Cut more off. For the sake of argument disregard the back branch for now, simply because I can't see it very well. If you cut the largest branch (right hand side) off you can see that it greatly increases both movement and taper. A split that high up is not appropriate for a twin trunk style.
It is also possible that you may be able to cut both of those off and go with the lowest branch as the new leader. Later, another chop to repeat the process, this is how taper is created.
This is the way most larger, and many smaller ones as well, bonsai are created, from the top down not from the bottom up. Seedlings, cuttings and young nursery stock can of course be used but they require years of growing out in order to obtain any girth.
Glad to see someone is taking this route.
EDIT: Oh, I missed that both shots are of the same plant. Are you saying that the larger portion is dead, or does that refer to another tree?