With a severe winter, you may have some dieback. In your area, after a few years, expect it to mature 8-10’ x 8-10’. To keep it smaller, prune it back each spring when you first see the leaves emerging. Don’t wait too long or you will cut off the flower buds. You will be able to control the height somewhat. If you want a miniature crape myrtle, take a look at Midnight Magic. It matures 4-6’ x 4-6’. I think it will be a better choice for a small space and easier to control the size.
Thanks for writing!