natal plum

I bought two natal plums a couple of months ago at a local nursery. I would like to plant them in the yard, but have checked Plant Files and see that they are only considered hardy to zone 9. Has anyone grown these successfully in zone 8b?

My neighbor in zone 8a planted one in full sun and has looked great this summer. She planted it this spring, so I don't know how it'll over-winter. I looked on plant files, and one person from Oklahoma has had success. My feeling is that natal plum should do fine in Austin.

Thanks! I'll get them planted this week, as we finally had some rain.