Just some thoughts on air pruning: Success is based on the willingness of the specific kind of tree to root. Trees like apples will root readily. Trees like persimmons take much longer to root if at all. The further south you are, the better your chances for success. Roots in bags above ground will freeze easily and die. Shorter growing seasons allow less time for root development. The more readily a tree roots the further north you can have success. This can also be done with branches, not just suckers. One trick I've seen (but not done myself) is to constrict the branch with a wire prior to injury and applying the medium. The constriction presumably causes auxin to be stored there increasing rooting.
Good looking project!
Jack