Following the thread drift re Cessna slips. Pre 1971 C 172's have a shorter dorsal fin and are more likely to show a tuck under and/or elevator pulsing. I have never experienced this in the later models only the early ones. That been said I teach the full flap slip is an emergency maneuver. Cessna's come downhill pretty well with full flap. If you are still too high even with full flap then instead of slipping you should go around and set up a better approach as the one you are on is outside an acceptable approach flight path.