What size do you think I might be after 800cc silicone sub muscular implants?

Unfortunately no one can adequately answer that question on this or any other website site other than saying that you will be very large.There are no manufacturers' standards for cup sizing in the
bra industry. The cups of a 38 D or DD and a 40 D or DD are significantly different. Cup
size varies from manufacturer to manufacturer and even within styles from any
particular manufacturer. Nor is there a direct correlation between implant
shape or size and cup size.

Keep in mind that following the advice from a surgeon on this or
any other website who proposes to tell you exactly what to do without examining
you, physically feeling the tissue, assessing your desired outcome, taking a
full medical history, and discussing the pros and cons of each operative
procedure would not be in your best interest. I would suggest that your plastic
surgeon be certified by the American Board of Plastic Surgery and ideally a
member of the American Society for Aesthetic Plastic Surgery (ASAPS) that you
trust and are comfortable with. You should discuss your concerns with that
surgeon in person.

Robert Singer, MD FACS

La Jolla, California

There isn't enough information to answer your question, but you will definetly be BIG!  You will certainly be atleast a DD, and likely bigger.  Make sure that is what you really want before undergoing the procedure.  Seek out a few consultations from a board-certified Plastic Surgeon before making a final decision.  All the Best.