Hey BP,

Can't really help with the performance as I have them on order for my Corban Icon. I think they must have sent them over from the USA by refugee boat as its taken ages and I am hanging out for them to get here. I did look everywhere to see if the came in FCS as well but couldn't find anything other than futures for them so pretty sure they don't do an FCS version.
Don't know about the sizes that you have on the FCs one's you mentioned but I have S25 medium quads on my shortboard and they work really well on it. I wish the Icon was FCS not futures so I could stick them on. They are bigger that the standard ones that came with the Icon and I'm finding the smaller fins make the Icon feel a bit loose. Maybe it has something to do with the 100kg / 10' board combo .
Good luck with whatever fins you find and hope they work for you.