Personally I would let it grow out a tad more, to at some point cut back to the 3/4 bigger subtrunks you got going on. Meanwhile make shure to work the nebari, maybe try the Ebihara Method, It leeds to great results in short time. Maybe plant it in a flat wooden grow box or anderson flat then. Once youre happy with the trunk size, cut back to the bigger subtrunks in early spring, wait for it to bud back out, let it grow a few months, hack everything back, repeat 2 times in the season, while fertilizing heavy. In Fall wire the branches some nice movement.
Trunk thickening will take 3-5 years, if you fertilize heavily.
The ramification building with the process I described will take another 3-5 years.
Then you will get something like this:
View attachment 563091View attachment 563092
Or of course you choose a different style, but I like the more tree like / naturalistic form on elms...
Cheers
Raffael