I am a firm believer in Tissue Based Planning principles. There is a growing group of plastic surgeons across the world that believe a 30% reoperation or revision rate 3 years after surgery for: size change, poor position of the implants, stretching of the skin etc is way too high. If a breast implant chosen is based individually and in a customized way to fit each patient's breast, based on a few basic measurements and assessments such as breast width, stretchiness... and an implant is designed to fit in this range, the results are very consistent, full and natural and do not produce stretching or problems and can lower the revision rate to 3-5% at 3-5 years. If any implant size is chosen, eventually it will place tto much pressure on the breast and skin and thinning of the tissues, increased malposition, wrinkling and rippling etc may occur. You are correct most patients and even some plastic surgeons do not understand that saline weighs slightly more than silicone, not less. In addition a saline implant is filled in surgery and does not include the weight of the shell of the implant...verses a a silicone implant that is prefilled and its' shell is included in the weight...so when I replace a 300cc saline implant filled to 330cc's it actually weighs 350grams/cc's so we need to replace with a 350cc implant just to get back to baseline. Finally the most common misunderstanding in choosing an implant size is that implants come in 30-40cc increments...patients cannot really tell the difference inside the body, particularly submuscular, between a 300 and a 360cc implant although 360 sounds a lot bigger. We have to add 100-150cc before you really begin to recognize the difference. Personally I rarely place implants, even in revision patients > 500cc...ususally this outweighs the tissues and further problems can occur. To directly answer your question, a 500cc implant is certainly larger than 350, but if you had prior saline implants your implants probably weighed 370-380cc bringing them closer to 500cc/grams. Most patients can tell between implants 100cc or greater...if your weight has changed this can also affect your breast size. Hope this helps.