I'm pretty sure I know the boat you have. It's a Nacra 6.0 original, not a North American. You have a Morrelli main and an EP main. The EP is the larger one for the N/A version. It simply has a bit more roach to it and generates a bit more power. In heavier air, you could break the mast if you don't upgrade to the longer spreaders and internal diamond wires. I'm sure it's the same mast extrusion as the N/A. You should contact Skip Elliot at E/P sails since he was one of the big designers along with Roy Seaman on this rig. Bullsheet on the square top crap. I sailed one a few weeks ago with a square top and ran the piss out of it. The mast did just fine with us double trapped. I would get the curved jib traveler track and stay with the jib configuration. The front spreader you have is the old version (round bar) and you should keep an eye on it and possibly upgrade to the foil type at some time. I have one for that boat if you're interested or you can get them through Murray's or Performance.
You have a great boat. If you upgrade to the longer spreaders and internal diamonds, they can be a pain to adjust. Get intouch with Rick Bliss from New England Catamarans for some inside tips.