Even if you get the same size, many bras and camis have buckles. Yes, you can wear loose and dark clothing to help hide it which may help against casual glances but not necessarily someone right next to you. There have been many stories here about getting busted by sight on someone laying a hand on a back or shoulder. The moral of the story, enjoy life and do what you want, but don't wear these items unless you are prepared to be caught as there are no guarantees.
