Your situation is difficult and will ultimately involve some tradeoffs. You are obviously thin and having your implant placed under the muscle would certainly help minimize a visible implant and upper pole rippling. Because your breast are more laterally positioned on your chest wall, you are at risk of lateral implant displacement with muscle activity, and that risk is certainly higher with a smooth surface implant. A textured implant will help reduce the chance of lateral migration although not a guarantee.
I would disagree with the statement that textured implants do not feel natural or necessarily not move in a natural way. First, it is important to specify whether we are talking about saline or gel implants. There is simply no question that in a person with thin tissues, a saline implant (textured or smooth) will feel the least natural, while a textured gel implant will feel much more natural. If we now consider the smooth vs textured surface issue, it is true that smooth surface implants usually end up having more mobility on the chest wall which might be considered more "natural". But in your situation, that increased "natural" mobility could very likely mean that your implant will "naturally" fall out towards your armpit, as natural breast tissue does, but that is just exactly what you are trying to avoid. So it seems that in your situation you will benefit from having an implant which is less mobile on your chest wall, and an textured gel implant would provide that benefit.
As to the question of high profile implant will make your breasts look closer together I would say that is not so. Mod profile implants are wider for the same volume, so if centered behind your nipple, they will extend further medial thus slightly diminishing the wide medial space. Of course they will also extend slighty more lateral as well. It is also important to not try to position the implant more medial to reduce the space between your breasts because that will cause your nipples to rotate outwards which looks very weird.
The issue of bacteria on the implant surface and biofilm formation can occur on both smooth and textured surface implants and has much more to do with capsular contracture. Textured implants under the muscle tend to have the lowest rates of capsular contracture.
The role of textured implant is primarily to reduce the incidence of capsule contracture. The textured implants do not glide as freely as the smooth implants because there is some adherence of the capsule to the implant surfaces. However in active individuals I feel the textured implants is a safer choice as the incidence of capsular contracture is considerably lower compared with smooth implants. Regarding the choice of MP vs HP implants this is based upon the look you wish to obtain. It is the width of the implant you choose that determines the closeness of the cleavage. i.e. the wider the implant the closer the cleavage. The MP implants are wider compared with the HP so the MP implant will give you better cleavage for the sizes you have chosen compared with the HP style. The down side is they are less projecting, so if you are fairly flat chested the HP style will give you more projection. I personally would recommend the MP+ style by Mentor as that style of implant has more implant fill and less chance for vertical rippling. Regarding your question if the implants may move over laterally, this is related to several factors. First the lower medial origins of the pectoralis muscle needs to be released surgically or there can be considerable distortion of the breast implant when you flex your pectoralis muscle. The less distortion of the muscle the less forces are present which may push your implants up and outwards. If you lay on your chest for prolonged periods of time such as sleeping on your breasts or surfing the pressure may stretch the implant pockets laterally and you will end up with implants that are displaced laterally. Its best to wait at least six months after your breast augmentation to begin surfing again. If you are too active after surgery you may end up hurting your breast and developing a capsule as a result of injury.
Correct positioning of your implants in the sub-muscular space will prevent lateral displacement whether they are textured or smooth. While it is true that textured implants move less than smooth implants, this is also a problem because they neither have a natural feel nor do the breasts move in a natural fashion. Recently published data show that textured implants have a greater propensity for infection than smooth implants because bacteria can cause a bio-film that is more easily hidden amongst the texturing of an implant.
Fortunately, you have several excellent Board Certified plastic surgeons on Maui. Choose a surgeon you trust and then follow his recommendations.
With reference to high profile vs. moderate profile implants, because your breasts are far apart and because high profile implants have a narrower base diameter, high profile implants will not make your breasts look closer at the 286-304cc range.
I agree with all the answers just wanted to add that it is very important that the surgeon limit his lateral dissection, this will also diminish the chance that the implnat displaces lateraly.
A sub-muscular breast augmentation has many advantages for you. The crucial point is for the implants to be placed properly in the sub-muscular pocket. With proper pocket placement and textured breast implants lateral displacement of the implants is not likely.
However be aware that your nipple areola is already laterally displaced. If the implants are placed to far medially that is towards the cleavage area and if the bulk of the implant is medial to your nipple areola that placement could further displace your nipple areola laterally.
It is crucial find a very experienced board certified plastic surgeon who has an excellent reputation in your community. Be sure to discuss your concerns about lateral displacement of the nipple and discuss with the surgeon that surgeons recommendation for placement of your implant.
Thank you for the thoughtful question and picture. I would agree with you that sub muscular (dual plane) breast augmentation will be in your best interest. In my opinion, more important than the smooth/textured characteristics of your implants will be careful development of the breast implant pockets; careful selection of your plastic surgeon therefore will be key. All other considerations, including activity restrictions after surgery, will be of secondary importance when it comes to issues such as breast implant displacement postoperatively. Careful selection of your breast implant size/profile also be important. This is best done after careful communication of your goals. This communication, in my practice, is facilitated with the use of goal pictures, under bra sizing, computer imaging…. I hope this, and the attached link, dedicated to active patients, helps. Best wishes.