GS-Alpha,
Absolutly correct, I didn't try to quantify what the odds would be for related shut downs, just mentioned that they can only make the odds of an IFSD go up, because any term added to the expression cannot be less than 0.
But some people have trouble with the fact that just because something is unlikely to happen, if it happens anyway it doesn't REDUCE the chances of it happening again.
If shutting down one made a second IFSD a lot less likely, you'd just take off then immediatly shut one down, because "a second shut down is very unlikely" complete tosh of course.