Here is the top cut out. I will make my top double layered just to make sure it isn't too thin. I am making mine a higher neck cut but it could be done in many different styles and cuts and still work for the style... besides if it doesn't work well for the style and works well for you it will still work.
It isn't about "being right" it is about having fun and making yourself look/feel pretty. Who cares if you aren't supposed to do ____. Do you look good in it? Do you feel pretty? Ok, then fine (so long as you have people who will be honest with you).