Thanks to everyone for suggestions on hanging round quilts. Summary:

• if the quilt is for competition, don't make it round. there appear to be no means of hanging round quilts which do not involve special devices or stiffening which will not do well with mailing, folding, etc.

• quilts which will stay in one place can be, depending on size:

1. stiffened with buckram sewn into the backing and quilted into the quilt,
2. hung using a sleeve midway and rings towards the top through which to run support from the board in the sleeve,
3. supported by a half-circle of stiff material in a special "sleeve,"
4. supported by wire (including from coat hangers), or
5. anything that works.