Way too small!  I wear a 36G. I bought a 36F and couldn't get it around my ribs.  I even tried a 2 inch extender and it was still extremely tight.  Exchanging for a 40F. Thank god nobody will see the size!

Got the new one in today and it fits great. Hoping it'll work for my dress!  I'll find out in a couple days.  Will update when I actually wear it.