That list you have is good, the Duke trees grown in northern cal do well in cold but like any young avo tree I'm Sure they were protected the first several years of young life, arivipia avo out of az is also reported to take cold but that's up for debate the mother tree is suppose to be in a very cold area in a canyon one guy tells me no that's a banana belt area so I really don't know for sure. I've had first year mexicola die on me in 23 to 25 degrees with only a cover on them, so when people talk about lower temps they should talk about how large the tree is to take those temps under 20. And also no matter what take extra care to keep the graft warm so it can come back after a hard freeze