I have not suspended the whole hood over the tank. However, desperate for a solution to my low-light/budget problem I bought a hanging dual fluorescent 48" shop light from the hardware store and hung it from the ceiling. It normally hung about an inch from the cover glass, but I used wire chain to hang it, so I could just re-attach it a few chains up while cleaning.
That gave a really neat ripple lighting effect on the wall behind the tank, and the plants loved it. (48" full-spectrum bulbs.)