Did a little experiment today. I took my right arm out of the sling and tried doing some sketching. 45 minutes later this is what I learned.

At least for me my pectoral muscles act to control and stabilize my arm while I'm drawing. Unfortunately this means even with a my right arm supported and not bearing any weight I am putting strain on the clavicle, and that hurts. So I am still out of the serious drawing business for a bit longer. But at least I got couple Petina sketches done.