I have two gc2b binders, my only complaint is how high the neckline is because I can't wear a lot of loose tshirts, and I live in Florida and am struggling to find high enough necked sleeveless shirts to cover.
Advice though, size up! I measure 36, but have big shoulders, so I wear a Large. I used to be a D cup before I started wearing binders, and I was tempted to get a medium, but I am glad I didn't because I wouldn't have been able to put it on. Get the right size and you will have a perfectly flat chest, no worries.