Sadly I no longer have any book of Torah [not the Avi Ezri or the Rambam or any Gemara] that I can use to look up anything. Still with what I recall vaguely, I wanted to answer a question on the Rambam. [I hope I am not forgetting anything.] In short, I simply want to say that I think Rav Shach supports the law in the Rambam in טוען ונטען פרק ו' בלכה ג by means of several factors. From what I recall each factor by itself would not be enough.
Therefore when the Rambam writes down the law of that we believe the husband when he says the wife he just married was not a virgin. The reason is simple. We can not say she was not מדקדק [careful in her words] when she is coming to ask for money. But we can say a person that is getting out of  a debt we can say he is not careful in his words.

That is all I have to say about this. But just to make myself a little more clear let me just add some background. The Rambam ch 6 law 3 of Laws of Pleas says: "A person comes to court and says you owe me 100 zuz. The other says in court להד''ם, I did not borrow. Then two witnesses come and say he borrowed and paid back. He must pay the 100 zuz because כל האומר לא לוויתי כאומר לא פרעתי "Anyone who says 'I dd not borrow' is as if he said 'I did not pay back.'" And the other needs no oath because teh borrower is already considered a liar." To defend this law Rav Shach needs R. Akiva Eigger, the Ketzot, the Netivot, the Ri MiGash and maybe some more people that I have already forgotten about.
How to condense this right now I am not sure of. But to be as short as possible let me just say he needs that "Anyone who says 'I dd not borrow' is as if he said 'I did not pay back.'" is not an open confession. It is simply a statement that implies the result. [As the Rashbam says about a different case in Bava Batra 34]. But in order to say that it does not imply the result automatically it is necessary to say he was not careful in his words as the Netivot says about the law one can go מפטור לפטור. [That is the exact same law except that the borrower changed his plea before the witnesses came]. But we can only say that he was not careful when he is trying to get out of an obligation, not when he is asking for money. How do we know this? Because of the fact that the Rambam Laws of Loans when the lender is not believed by a migo when he changes his plea from it is a good document to the document was forged but I had a real document and it was lost. I am  forgetting a lot here. Still I think the point is clear. So when he comes and says פ''פ I found an open opening, he is believed even though she has a migo that she could have said משאירסתני נאנסתי. But why should we not believe her. Do we not say a migo?  And a person can go from פטור לפטור. The reason is she is not going from פטור לפטור but asking for the whole Ketubah.

Maybe I will be able to look this up someday I hope.