Trees, Shrubs and Conifers: What is that called?, 1 by wormfood

wormfood wrote:
A method of propagating evergreens, where you scrape the bark off the branch, cover with spagnum moss, then plastic wrap and wait for roots so you can cut the branch and have a small tree.

I have a large tree that is doomed and it's probably too large to move, so I'm trying to save it through other methods. I have 6 small branches done (when I noticed eyeballs staring down at me- bluejays with babies) branches about as thick as my thumb.

My question is how large of a branch can I do?