I realize this thread is 6 months old already, but thought I'd chime in.
I've never been able to "summer over" my Pac G's either...but for the past 2 years I've been successful. I always treated them as annuals in the past, but our past two winters have been much colder than usual. I stopped directly watering them in the summer, but mulced them heavily when they were dormant, covered them with a large pot, and they came back. I was shocked. Same for the P. obconica's which are in the same spot.
Our summers are also hot and humid, but it worked like a charm. Here's one grouping of them.