I know others have recommended citing the PWA, which I would absolutely try but just an anecdote from my experience:

I went through PenFed and the people that did my mortgage didn't wanna see the PWA. I even sent them a PDF of our pay tables but they said no too, even though it would've answered all their questions. I had jumped from year 1 to year 2 right as the new contract hit and they were "suspicious' about my drastic pay raise. Only thing that worked was providing more pay stubs.