I am reading a small book on the proper use of Iron Condors (link). I do not use these strategies as I have had a very hard time being profitable on them. This book mentions some strategies to creating an Iron Condor I didn't consider.
I am trying to understand the following statement:
Selecting short strikes at a particular level of delta exposure allows the width of the iron condor to change automatically with changes to Implied Volatility.
I understand how IV effects the price of options - however I am confused at the use of the term "automatically adjust". Isn't the width of an Iron Condor fixed at the difference between the two short strikes? How does selecting say, the 40 delta strikes, help the Iron Condor deal with Implied Volatility? The author implies this is some sort of automatic risk factoring being done. It seems too good to be true, which means I am missing something here.
I'm interested not only in an explanation but perhaps some mathematical treatment to this as well. I find this very interesting.