I wish there was an option for actually flat chests - I wanted to create futa presets to stand in for males in the types that don't have them, for a bit of variety, but the way the textures are done there's always a shadow painted on like the breasts are there. It makes it difficult to make smaller boobs look right too, but it's less noticeable when there's at least some shape. The only way to get rid of the shadow is to shrink the size until the areolae and nipples are invisible as well, which is a weird Ken doll kind of look, and it's not possible to make those enough to get them to show up afterwards. I'd give a lot for an attachment or variant that just slapped the male chest textures on there, even if it was locked behind creator mode or a menu option to avoid it spawning in when not wanted.