At least on my nacra 6.0, which has already inverted the mast once, I bent it back, I use the downhaul to help 'protect my mast and provide some extra 'backstay', along with leaving the mainsheet fairly tight and just using the main traveler.

Incidentally, what I thought was a totaled mast, now sails better than ever!

My point-I use the mains downhaul, because I thought I was protecting the mast more. guess I don't really have things figured out?