Quote from rdemyan:
I've been doing some analysis on this and it seems like it would probably be preferable to use indices that don't have next morning expiration (i.e. SET for the SPX), particularly if these straddle/strangle swaps are put on within the last week or two.
So as the underlying moves away from the peak on the expiration curve, the adjustment would be to buy back the straddle and sell a new straddle that moves the peak in the direction the underlying is moving (repositioning the tent pole).
Is that correct?
Although I'm no expert in double diagonals / straddle-strangle swaps, I've done some work with them.
Why would you want to trade them close to expiration - to increase probability of landing on the short strike? If you go out in time (say post expiration week), then you may be able to collect more premium on the short straddle thus reducing risk - but the underlying has more time to move out.
Other point about moving the tent pole up/down depends on the availability of strikes and your long strike selection and the underlying's behaviour. Some may choose to just close the whole trade around breakeven (depends on vega action at the time) if the underlying moves out of the profitability range.