When trying on your new DUI drysuit, make sure it allows you to change your insulation for varying water temperatures and exercise levels. At all times the suit and insulation combination should keep you in your "comfort zone."
Wear the thickest insulation that you will use and test for full range of motion.
There should be absolutely no restrictions during deep breathing.
If you haven't worn a drysuit before, it is an acquired feeling. At first, it may take a little extra effort to dress in and out of, but over time this process becomes much easier.