I agree on the FCS key. The Starboard SUPs come with them, so it would be easy to include them with the Quads too. Anyway, a 2.5mm metric will do, I believe, so its not that hard to find even in Europe.
When the fcs fins are new, the can work loose a bit, so after a short session you might have to go in to tighten them. After my first session they have stayed in place.