The Vega curve of an ATM fly resembles a smooth "S" if one looks at minor price moves (1-2%) and looks like two mountains on both sides of a valley if one looks at a bigger price range (-10% to +10%). Is there a way to Vega hedge a fly so that its Vega curve becomes an: 1) almost straight line OR 2) reverse it's Vega profile so that it's a reverse "S" shape? In the real world, do you rehedge Vega risk once it gets above a certain threshold, or is the hedge static and held all the way to expiration? Thanks!
A butterfly is already a hedged position, how much more hedging do you want!? I mean, the more you hedge the less is your return. If you want a flat vega profile then don't trade options. If you want to have an inverse vega profile then just do the inverse trade.