Like crape myrtles, they will take severe pruning. You can cut them so severely you could almost classify it as pollarding. I don't like to prune anything in winter. I always wait until the leaves start showing tiny green buds. In zone 8 that should be about 3-4 weeks.

I just came inside from pruning my hedge of rose of sharon.
They were well over 12'and spresding too far into the flower beds, now they are 7' and lost about 1/3 of their width. I have prune them back this hard one other time, about four years ago.

One question thou. How can I control the seedling problem?
every year I must pull over 50 seedlings that start to grow in the flower beds.