Here's one article about postnups. Just copy/paste.
Wiki has good info:
This from a CA attorney but good advice:
This article has several case studies:
I will say a good attorney would be able to question part or all of a postnup in court. With the help of a friend from SI, I was (pro se)able to have FT's attorney question to the judge if we should throw out our post nup and start over.
Needless to say FT honored it at the end and I received my money and then some extra by the end of the divorce.
The post nup is only as good as each spouse honors it.
Hugs do your reseach for laws of your state.