Hi Doug, I had a Hobie 18 for about twenty years and I have raced with Smythe sails on an F-28R. Smythe sails are normally cut relatively flat so I think that prebend would be a poor set-up decision unless it is always very windy where you sail. A better decision is to have at least an 8 to 1 downhaul to bend the mast when you want and to keep it straight when you want full power. Since you have specialty sails from Smythe (not class legal) you should get rig and trim advice for using those sail from Smythe also.

Have fun!

Mike