I know various measurement issues have been covered in other posts....but heres what I'm worried about....I have a bit of a tummy....about 48" standing when my hip measurement is about 51-2"

sounds about right for waist to hip ratio but heres the thing...when I sit the tummy goes from 48-50ish?

If I measure for 48" won't i then suffer...the oh my goodness I need to loosen the buckles experience when i sit down?