This is a little off the topic and I thought about posting it under the recent Twinzer thread but this should work. One way to figure out what fin system works better is to cut a hole in a perfectly good board. The following pictures are of SC Surf modifying a Mitsven Magic with a 2+1 fin set up to add Twinzer boxes for the rear fins. He is using Futures boxes because has the template kit for Future fins and Future Twinzer fins. His fin placement is based on a Mabile Honey Badger with a twinzer/single fin set up. The pictures are up to the point where the rear boxes are in. Next steps are glassing/finishing. If you have any technical questions on how he did I it and why, I suggest you DM him or ask the question in a reply and I’ll ask him to take a look.