Can't answer your questions, but I've wondered if one can graft an edible Persea americana onto a super-hardy Persea borbonia rootstock.

As long as the grafts are good you will get a tree that is the top part graft.

You will have to keep the rootstock warm by heating it or insulating it or it will die if the temperature goes below its tolerance level.

Steve

Frankenstein avocado tree

https://www.youtube.com/watch?v=9cVjwSmHT2I

Multi graph 8 varieties

https://www.youtube.com/watch?v=D7jMtUJmMGQ

does anyone know the most common root stock for cold hardy Mexican verities that wholesalers use?

I have a Mexicola I'll be planting this spring.

Does anyone know what winter hardy Avocados are not patented in case I wanted to sell a few each year from cuttings?