First, you have to reconsider using cup size as your measurement since this can vary depending on what brand of bra you wear. Next the implant you choose should fit within the measurements of how wide your breast is. The larger the implant the more your breast will take the shape of the implant and the less natural it will look. If your breast is narrow you may only be able to fit a higher profile implant if you are looking to go into the 400cc range. The most important factor is to have an implant that fits your measurements. If you use an implant that is too large for your breast to stretch into then there is a much higher risk of developing complications of shape and nipple position distortion later on. Also you are at a higher risk of getting visibility of the implant in the form of rippling the larger you go.