I have a large band size (40) and a small cup and if I could go down to say, a 38 of even 36, I would have a much larger choice of bras.
I could use an extender to fit a 38 bra to my size, but would it work? I am worried about cup size, the space between the cups and also that the extender would set my straps too far apart, leading to embarrassing dropped strap problems.