I have a 32 foot long Tornado carbon mast on my Nacra 18 square, it is very light and easy to rig, stiff enough to hold the square top sail up and I'm very happy with it. The down side of finding another mast is the rigging points may be in a different place and you can't just pop rivet new attachments for the hounds, the fitting will probably be something that is manufactured to slide inside the mast and be resined in place. I just got different stays to suit the mast made, good luck with your project

Each catsail has a curve in their frontleech. So its not a straight line but there is a point where the curve is at its max. This is called the external camber of a sail. Hoisting that sail in a straight mast track will always cost you extra force because the frontleech doesn't follow the straight line of the mast. The greater this external camber is, the more trouble you will have with hoisting.

When you bent the mast with spreaders you will make the effect of the external camber again smaller. But don't forget that only this external camber will create the vortex of the sail when pulling the downhaul!
So only because of that your sail becomes the aerodynamic motor you want it to be.

P.S. external camber may never be negative; that's why sailmakers often cut to much camber in their sails. In fear of too much bend masts.