Really don't have an answer for your questions, but there are also some large ones in Spring Grove Cemetery that tend to be stem as well as root hardy

There are also some planted at the Friendship Park, along the river. You might try contacting the landscaping department for the zoo or park to find out more about the variety of Crepe Myrtle they have planted.

I think I will try to contact the horticulture department at the zoo and see what they have to say.
I can't imagine that temperatures are too different between Spring Grove and where I live.
My wife really likes crape myrtles so I'd love to have a nice one in the yard.
Thanks for the replies!
Bob

Let us know if you find out anything. I love these plants also.