Hey Martin, One thing that may help with the stress on your elbow is keeping your bottom hand low. One thing I tell my students to do is to put your paddle over your head and make 90 degree angles with both arms like a goal post. It may feel like your hands are a little far apart at first, but you'll notice it puts a lot less stress on your joints. Remember technique and finesse can really make up for brute strength.
Have you watched any of Jim Terrell/QuickbladePaddle's YouTube videos? Great info!