troy, You should have no problem sailing accross the bahama banks with 6'' of draft.
The beauty of a swing keel is that it will pop up once you hit something, either a coral head or a sand bar, as long as it''s not held in the down position. You can always lower the keel to the 5'' or 4'' foot depth, and still make decent headway as needed. In water that shallow in a breeze, you might not want to sail anyway due to the wave action in shallow water???? You would probably be motoring at that time.