I've tried several methods, none of which appears to alter the subluxation 'gap', clinically. Cannot say radiologically. A collar and cuff is barely useful and probably causes more problems than solves. If you can obtain compliance- hereis what I do:
Request the sling is ONLY for transfers. It must come off and the arm positioned if sitting and lying.
Make FOUR loops in the sling. Two for above and below the elbow, and two for wrist and hand support. This way at least the support to the head of humerus is directly where it should be - under the glenoid cavity, and kept there by the loop above the elbow.