每日吃瓜

Ive got some great candidates in my yard for air layering, a few of which are some large flowering black locust trees with some pretty low hanging branches - I havnt tried air layering before but it sounds pretty straight forward. I guess my question is how thick of a branch should I be aiming for and how long should I cut the branch down to? The trees are all full grown and on my property so I can get to some pretty chunky branches, but also curious about length after the roots grow - im assuming the pretty mature branches will not be willing to bend with wire? Thanks for the tips