RE: Double fins?
Unless your winds are straight onshore, try learning to sail your board backwards (fin first).
It's easier than you think it might be, and when you sail with your weight in front of the mast foot, the tail is lifted quite a bit and you can sail pretty well in very shallow water.
The Formula guys all do it, and I've found it to be quite easy as long as the wind supports going away from the beach or back to the beach on your way in.
Hope this helps,