Is 745 cc too large ?

Those implant sizes sound a bit too big for virtually any patient. Assuming your skin is a bit stretched from the weight loss those implants would accelerate tissue stress Consider going smaller and tightening the skin with a mastopexy 

It is very difficult to determine the best lift you will need (recommended based on your photos) or the exact size and shape implant you will require to best match your ideal breast image without an examination by a board certified plastic surgeon. Not just any board certified plastic surgeon, but one with many years of frequently performing breast augmentation surgery including different approaches, techniques and implant choices. This is because several measurements not to mention your breast characteristics are needed to determine the optimal implant size to obtain your goals. Without knowing these dimensions it would be difficult to make this determination. For example, the existing base width of your breast will determine, in many cases, the maximal volume per implant profile that you can accommodate. To illustrate; a 100 cc difference may make a significant difference with a narrow base width breast, but much less of a difference if you have a wide chest wall and wide breast “foot print”. Therefore, just because your friend may have a great result with let’s say a 300 cc implant to make her go from a “A” cup to a “C” cup size does not mean that you will have the same result with the same size implant. The same process goes for just filling in the upper part of your breast without becoming much larger. Further simply placing implants in a bra to determine the size best for you is not always accurate as the bra often distorts the size, is dependent on the pressure the bra places plus the implant is outside your breast and not under it among other variables. Computer software morphing programs that automatically determine the best implant size can be helpful in some but not all cases (e.g. doesn’t work well in my experience with existing implants, sagging or asymmetric breasts). Using “want to be” photos however are useful if simply provided to the surgeon as I will further explain in the link below including silicone vs saline implants

#Breastimplants come in a variety of shapes, sizes, and profiles in order to offer a custom-fit and natural-looking physique. It is also important to consider the substance and texture of an implant. In particular, those implants approved by the U.S. Food and Drug Administration (FDA) are filled with silicone or saline. These materials impact the feel and look of a breast implant, and thus are an important consideration in determining the desired appearance of your breasts.We aim to custom-tailor breast augmentation based on patient preferences for perkiness, firmness, shape, and size. Our goal is to match the appropriate implant type with the right procedure so that you are completely satisfied. Breast #augmentation will enhance the shape of your breasts as well make them fuller. You may find yourself more comfortable wearing different types of clothing and may enjoy a boost in self-confidence, as is the case with many happy patients. Now, it is completely up to you for the final decision of your implant size, but it should be discusses with your surgeon in consultation in order to make sure that you place comfortable expectations upon your final results. 

This question is almost impossible to answer without a good examination by a board-certified plastic surgeon. There are many variables that will determine the final aesthetic outcome, and no certain volume is the best for any given patient. Perhaps try on some sizers to determine what best fits your body and expectations.

Without pictures and an examination that is a difficult question to answer. Just because your chest wall can accommodate a large implant doesn't mean that is your desired look. Discuss your concerns with your surgeon and if you still are uncomfortable seeing a second surgeon for another opinion may help. Good luck with your surgery!

Hello and thank you for your question.   The size of the implant is based on your desired
breast size/shape, your chest wall measurements, and soft tissue
quality.  This decision should be based on a detailed discussion
with equal input from both you and your surgeon. 
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon