My NACRA has a boomless mainsail. Its one of the things I'm disgruntled with. When the wind gets above 20 kts the bottom two battens quite regulary 'invert' ruining the shape of the sail. You have to back the main sheet off to get the battens to pop the right way around. Boomless is fantastic when you have kids on the boat but I don't think there are many other advantages.

The performance NACRAs have a boom - F18 and I17?

BTW I'm still thinking of the terrific sail I has at Eden on Phillip's mozzie. My 4.5 is for sale hope to get a Taipan or maybe a Mozzie by the start of the winter series.