Will 400cc hp silicone unders be too big for me? (Photo)

The size should fit your anatomy, make sure your surgeon has picked an implant that matches your tissue dynamics so you can have a succeful long term outcome

400cc will make you a full D or DD. As long as you felt comfortable with the sizers on during your consultation, I believe you will be very happy with your end results. Please also do not get caught up in cup sizes as cup sizes vary as your chest band size changes. i.e. a 34D is going to be significantly smaller than a 38D.