I've watched this thread with interest as I also enjoy elms. Something has been bothering me though, and it's time for me to pipe up!
Firstly, good job so far mate. I think you have grown the tree pretty well. As elms are fast growers and typically apical ly dominant, I think it's time to ask the difficult question, and potentially take a plunge to get this tree looking really good. The suggestion is simply, from what I can see of the tree's early development, it is a bit taperless and the trunk is very thin higher up. Elms grow like stink, so, were this tree mine, I'd consider cutting it down by about 30% in height and then just let all branches grow uncut for a full season. This will do two things. Firstly
it will make the tree look rubbish for a while, and secondly it will with a stroke of luck make the trunk thicker relative to the tree size. 
You can regrow the canopy in the two years that follow while cutting back the entire tree hard in the dormant period, or potentially twice annually if it grows strongly. So the reason for this treatment is to improve the tree's trunk thickness relative to it's branch structure, which gives a better impression of age, while at the same time getting good taper and shape to your branches. Of course this is best done in a growing on pot.
Here's a link to my competition elm. Take note of how I cut back hard for good basic structure early on and grew from there. I think you can improve this basic structure in your tree. viewtopic.php?f=140&t=9055
Cheers,
Andrew
