i think that sleeve rule is changing in some local guild shows that are mainly art quilting based.
the national and large shows still have the sleeve rule.
since art quilts are becoming very popular many shows allow for a framing on the back to hold the quilt shape and then you just sew on the sleeve across the back for hanging.
this is the main reason why i learned to run flexible wire or plastic all along the back of the quilt with tabs to hold the odd shape and then i just sew on the sleeve for the shows.