You could try some trim tabs...they'd probably solve your problem.
They look like these here, but minus the part that goes down. [link=http://www.offshoreelectrics.com/rc_boats/triton_boat/triton3.jpeg]trim tab pic[/link]

That is a pic of a trim tab/turn fin combo piece. Yours would just look like an "L" from the side. You can make them yourself for under $2. Go to your LHS and pick up a small sheet of aluminum, and cut out a piece that's about 1'' X 1'' and bend it in half. Drill your holes, and mount it to the trailing edge of your transom (the bottom edge where it meets the bottom of the hull) and your done.

Good luck, let us know how it performs!