Probably not? You might not get the full hop utilization that you would get with them fully immersed in your wort. Don't know enough to say for sure, and I haven't tried hopping in a bag to know if there's a difference or not.
Something that I just thought of - copper is supposed to be good...
Try putting a couple of glass marbles in the bag with the hops. They'll sink the bag to the bottom. Don't use "steelies" - they can have oil, grease etc on them.