Questions about setting up diagonals & double diagonals

[sonoma]

I have gotten myself wrapped around the axle on "long vega" trying to imagine why one might want this characteristic in a bear spread. I am conditioned to think of volatility dropping as the underlying rises, so long vega could seemingly make it difficult to get out of a bear diagonal without taking it in the shorts when the underlying moves up. I worked myself into a position where I thought long vega on the bull spread and short vega on the bear spread might be the optimal setup if one is a "defensive" trader, and I don't think that's correct.

Any further thoughts would be greatly appreciated!

Try thinking about a diagonal in an alternative manner: to enhance, not hedge, your reason for adding the trade. For example, if the underlying is sagging and your existing position is generating long delta, you'd normally want to add some short delta. You could do this with a long put diagonal. There's no need to "hedge" the diagonal because the existing position acts as your "hedge" - you already have more long deltas than you want - that's why you're adding some short delta. If you use the put diagonal in this setting and your underlying continues to sag, your position will often improve more than you'd anticipate because of the long vega. And if you choose the strikes properly, you can construct the trade to eliminate risk to the downside.