Thank you for your question. From your front view in a standing position, it appears as though you have a pleasing result. If you want to keep a natural appearing result, i would not recommend going larger. Not to mention the larger you go, the more stress you put on your tissues, and the increased chance you have of developing more displacement. If you did go a bit larger, I would recommend you not add a larger diameter implant, but increase the projection of the implant, although i don't think it will look as natural. In my opinion, 400cc would be way too large for your frame. With regards to the lateral separation of the implants when supine... it is certainly not uncommon. In reality, any sizable breast without implants will fall to the side to varying degrees. How much an implant will fall to the side, will depend on many factors such as the shape of the rib cage, the size of the implants, the extent of the pocket made by the surgeon, your tissues and capsules thickness and integrity and ability to hold an implant well in position. Some tissues heal with laxity and thin capsules that do no hold an implant as secure as others. Some tissues and capsules have great integrity and heal at a more ideal thickness and consistency and are able to hold the implant in an ideal position. And then, on occasion, there are those who heal with excessive thickness firmness and develop capsular contracture to have the opposite problem. Combine a narrow and oblique rib cage, and tissues that have a tendency to heal with laxity and thin capsules, the implant is sure to fall more lateral even if the surgeon creates a perfect pocket. There are many things the surgeon can control, and there are several unknowns and things a surgeon cannot control and has to use his knowledge, experience and best judgement to provide the best chance for a great outcome. The lateral displacement that you question, can be revised by lateral capsulorrhaphy ( lateral capsule repair ) which may or may not necessitate use of an acellular dermal matrix, such as Strattice, to reinforce the repair. These are all discussions you can have with your plastic surgeon. Best Wishes. Dr Sam Gershenbaum.