If you don't mind having some extra cabinets over your island ... I'm going to mount a row of upper cabinets over the island, elevation 72" so most of us can see right under them into the great room(that's my point in having an island anyways!) ... Just make the center 36" of the cabinets 3" (or is it 6"?) less in height and install a regular wall hood there ... duct thru the ceiling.
Put a piece of finished 1/4" plywood (cabinet quality, eh?) behind it all for a finished product.
Cabinets + ductwork + hood much less than island hood alone.