Don,
On my Zelkova...
The pipe collar is an experiment on my part to see if it will suppress the bulging that already occurred, and keep it from getting worse. I showed the pictures of my tree to Boon, and he said it probably wouldn't help. Rats.
Now, the root work is something altogether different!
The plywood was kept in place when I potted it up. That's the whole point... the plywood is screwed onto the bottom of the trunk of the tree so it can't move. Then, when the tree is stable, the roots can be spread out flat. I used screws to position the roots evenly around, and the screws are just holding the roots in position. They aren't thru the roots. You could use nails instead. Boon said I should have been more aggressive on my root pruning. That is, I left too many roots on when I did this.
But the tree survived and grew out well.
HOWEVER, Boon suggested that I prune all the major branches back to about 1 to 2 inches! Right now, from where the branches begin on the trunk they grow up about 6 to 8 inches before any significant branching occurs. I'll never get good taper in the branches. So, I need to do a major chop on all the branches! I'll do this after I go back to Boon's in late January.
Boon found a photo series of a Zelkova in Contempory Bonsai showing the process. So, as much as I like having a decent broom, it will not be as good as it could be unless I cut back those branches.
I will remove the pipe clamp, and take some pictures of what it looks like now, and then this spring, I'll update it with the "post-chop" photos.
Thanks for asking!