Choosing an appropriate breast implant size depends on a number of factors including your goals and preferences, the size and shape of your body and breasts, the quality of your skin and breast tissue, and the type, profile, and location of the breast implants. In general, 750 cc implants are considered quite large. I would not be able to make an assessment without an examination, but I would be concerned that the implants might be too large for your frame and that there may be increased long term risks including tissue thinning, stretching, and sagging. I would discuss your options with your plastic surgeon.
Larry Fan, MD
Web reference: http://www.bayarea-plasticsurgery.com/breast.html