Are we talking to Ira's people? You have come to the right place. One of the best persons to talk to is Sean Hogan, who owns Cistus Nursery. Their motto is "Your Home for Zonal Denial". He is in the forefront of trialing what works in this climate.
Myself, I recently moved from the Idaho mountains. Both here and there I am regularly planting beyond my zone and definitely getting away with it. As with California this winter there are extremes that take their toll but they are exceptional years rather than regular.
We haven't had what was considered a cold winter since 1990, in my opinion.

Here is a link that might be useful: Cistus

Yep, you're talking to (one of) Ira's people. I'll look into Cistus Nursery, thanks for the heads up! Send us a pic of your outside-zone plantings, we'll post it online.

I've had Poinciana gilliesii from Arizona in my Portland yard since 1988. It's got nothing to do with global warming. I placed it in a sheltered southwest corner next to the house, where it does not get cold winds, and does not get quickly thawed by the morning sun.

Another guy to talk to would be Jerry at Jungle Fever Exotics in Tacoma. Nursery and residence are adjacent, make their part of the street look it's in Waikiki.