Fish spin well, and trim down the line. They can take a high line. The turning ability gets really hampered if you get much longer than 6 foot (switching rail to rail is all foot driven). A longer board with nearly parallel rails, a deep swallow, and two keel fins will be a twin fin board, it just won’t feel fishy. If you are concerned about such a short board, you can optionally make it really really thick! http://www.blakestah.com/fins/