i own 2 f18 sails that i have used on my mystere 5.5 (30' mast)
a gen 1 and a gen 2 capricorn sail

they worked well, were very powerful upwind but lacked size for downwind sans spin
(the sail is designed to be used w a spin downwind)

i like them both very much but don't use them anymore unless my main is in the shop getting repaired