Peter,
I use a 2x2 piece of hardwood (Oak or walnut)cut at a slight angle. Place the knife edge under the trim and using a deadblow or plastic mallet (Rubber is too soft), strike it upwards starting on the front end loosen the trim slightly along the length. This will minimize the bends as you lift it off. Then go back and carefully tap it upwards until it releases from the fin. The tail end can be tricky, so take your time and you will stand a good chance on saving your moldings. Sometimes heat from a heat gun can help release the glue. Careful of your finish if that is a concern.