Hi Andy - I think two main ideas might be a good place to start.
Because you live in a fairly northern latitude, your refinement techniques (primarily decandling) will differ a bit from the approach taken in southern climes. Decandling, however, is likely a number of years off, depending on how big you want these trunks to become.
The second idea is that the main order of business at this point is thickening the trunk. Lots of fertilizer, no decandling and progressively larger containers will get you there fastest.
The big thing to consider at this point is what part of the trunk needs thickening and what shape the trunk will take.
Wiring and/or shaping should happen before thickening to avoid heavy bends later.
As for the placement of sacrifice branches, if they are all near the top of the tree, the entire length of the trunk will be the same diameter. Lower sacrifice branches will help with the development with taper. Will look to do a post on this soon.
That's some ABC trunk development info. Let us know if you have specific questions about these trees and we'll see what we can do to help.