Pam, I haven't tried it but my first thought is this wouldn't work well for you in Z5 (or even Z6) where b. davidii should only be root hardy and will behave like a herbaceous perennial.

The only plant I've ever invested time in to grow to a standard was wisteria, and the attention that required got a little stale over the years...a vine that clearly did not WANT to be a tree.

Morz,
All my butterfly davidii are extremely hardy for me...I've never had one die. Are you saying I couldn't select a single new stem on this year's growth, keep prunning except for the tip, and get results?
Thanks

Die, no. Die back - yes, I would expect it to die back (have cold damaged top growth) in winter in your zone. When your plant is young, you'd remove all but the strongest, straightest stem, then stake the single 'trunk' and when it reaches the appropriate height, remove all side branches to the point where you want the 'trunk' to branch out....continue that maintenance throughout the growing season. There wouldn't be much point if the upper parts of the plant are going to freeze back in winter, but you wouldn't have a lot to lose if you felt you'd like to try :)

They are evergreen here and not the tidiest of shrubs even when hard pruned in late winter. (If I'm not mistaken, b. davidii has also moved up a notch recently from Class C to Class B on the noxious weed list in this state for the self sowing habit.)