I'm considering changing out the Fatty on my Cannondale to something in carbon when finances allow. The Fatty is kinda unique in its dimensions: 395mm axle to crown and 53mm rake. The closest carbon fork I've found so far is the Enve Cross Disc. It is also 395mm axle to crown, but the rake is a shallower 47mm. IIRC, a shallower rake means increased trail, so the bike should be a bit more stable at speed, though I'm not sure yet if that's needed for the 'dale.