the NCX from what i have seen is a GOOD sail from Severne
if you look at unifiber website , forums, etc, Severne is HARD TOP
this means MauiSails, Gaastra and Severne masts will suite the sail the best
from the charts i saw, the luff is 494 and they are still recommending a 460
as i am a heavyweight and already have a hard top 490 - i would try the 490
how much carbon??
some pros say `as much as you can afford`
personally feel that us average joes can easily get away with 75 % and have a blast
some pros even use 75 % on race sails with cambers...
hope this is a start, but any Severne dealer should be able to help you further
good sailing !!!