Watch the Get Physical online guitar lesson by Brad Carlton from Chord Studies: Evolving Blues Vol. 2
Here's a great blues progression in D that uses a lot of great big dominant 13 chords. Try moving your elbow outward when working on the D13 as it will help you get the stretch as well as keep your fingers upright. Then, when you come to the C13 your elbow will move in towards your body, and the hand on the fretboard takes on a more diagonal shape. Thinking about where your wrists and hands are will help you get these chords sounding clean.