The extenders are a great add on to the minis if you want your feet slightly away from the tire. You feel more locked in having your foot placement a little more centered on your footpads while still having contact with the fins.
Great setup and they really helped me out.
I have the Flight Mini for Ambidextrous reasons, these extenders game me the extra support. Now I have the lock in feel of regular flight fins, but I have the ability to switch easily. Or have friends that right different from me ride my board. Which is great because I ride Goofy style, so friends can hop on and get the lock in feel too. Would buy another set for my future Onewheel, except that will be a full flight fin combo