What is the diameter for a mod plus overfilled saline implant that’s 1200cc? Currently 700cc UHP wanting to go larger.

If you currently have ultra high profile implants and are changing to high profile, that is going to be less narrow since you are decreasing projection. Also, typically implants are not overfilled to the degree you are talking about. For example, an 800 cc implant may be overfilled to 900 or even 950 if pushing it, but not 1200 cc. Implants do have limitations, and so does your body. I would not recommend going that large, because it puts a large amount of stress on your tissues and rib cage, even leading to rib cage deformity. When a patient feels their body swallowed up an implant and it is not adequate in size, typically this happens in a heavier patient with a broad chest and wide breasts, where truly the proportion is not fulfilled by standard implant sizes. However, in your case, when looking at photos you have posted, you do not fit this description, and in some of the photos it looks as if you already have the max size your body can fit. Your question makes me worry you have kind of lost sight of your size in relation to your overall proportions, though without seeing you in person, this may or may not be accurate. I think you would benefit from an in person consultation with a board certified plastic surgeon.

Thank you for the question.   Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:Generally speaking, every patient undergoing breast augmentation surgery should understand that their anatomic starting point will limit the outcome of breast augmentation surgery.   In other words, a patient's starting anatomy will limit how large of a breast implant can be utilized safely. The use of a larger breast implant (than what is safely "allowed" by the patient's anatomy) can be problematic;  potential problems include breast implant displacement/malpostion issues ( such as bottoming out, lateral displacement, symmastia...)  and/or significant breast implant rippling/palpability.

1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals.  In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. For example, I have found that the use of know words such as “extra large” or "DD cup” etc means different things to different people and therefore prove unhelpful. Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup size may also be inaccurate. Again, the use of computer imaging has been very helpful during the communication process, in our practice.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery, after the use of temporary intraoperative sizers.
I hope this helps. Best wishes for an outcome that you will be very pleased with.