Realistic outcome of high profile 415cc silicone round under muscle with my body shape? (photo)

 Congratulations on your successful weight loss.
 Based on your photographs, I think that you are starting at a good place and should have a very nice outcome with breast augmentation surgery.  It is difficult to tell, based on the single photograph, whether revisionary breast lifting would also be helpful.
There are several steps taken to select a specific size/profile breast implant for a specific patient.   These steps will vary from one practice to another. I prefer to have a wide selection of implants (all profiles) available in the operating room. I use intraoperative sizers and place the patient in the upright position to evaluate breast size. Use of these sizers also allow me to select the breast implant profile (low, moderate, moderate plus, high-profile) that would most likely achieve the patient's goals. The patient's goal pictures are hanging on the wall, and allow for direct comparison. I have found that this system is very helpful in improving the chances of achieving the patient's goals as consistently as possible. Ultimately, careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) will be critical.
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:
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 words such as “natural” or "C or D cup” or "roundness" 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.
In your case, my best advice: more communication. It will definitely worth spending more time (prior to the date of surgery) with your plastic surgeon to discuss further.  As you know, it will be important for many reasons, that you feel comfortable that you and your plastic surgeon are on the "same page" prior to proceeding.
I hope this helps. Best wishes. 

Patients often think in terms of cup size when considering
augmentation. Unfortunately, devices are sized in terms of milliliters (cc) of
volume. This can lead to some confusion when sizing. Additionally, it is
important to remember that cup size itself is not standardized with variations
from one manufacturer to another. Unfortunately, as many women can attest their
cup size in an industry leader such as VS is not necessarily transferable to
another brand.
Another point which is often under appreciated is that of
anatomy and starting point. Any implant will add volume to the volume which is
already present. The implant is additive. A particular volume will not
necessarily confer the same cup size to different patients (often times it will
not even confer the same cup size to different breasts in the same
individual...remember they are "sisters" not
"twins"). 
A general rule of thumb is that 125cc can represent somewhere
between 1/2 to a full cup size increase. Smaller volume differentials (25-50cc)
are typically less consequential representing a volume change of less than
a shot glass. However, I have found these numbers, at least anecdotally, to be
of little help. Patients often present with notions/goals which do not
correlate with these sorts of sterile volumetric assessments.
When sizing patients, there are a number of useful tools
including:
-3D imaging (has the added benefit of offering a volumetric
analysis of the pre-operative breast)
-Breast sizers (rice bags)
-Goal photos
I also recommend that patients commit to a particular look
rather than a cup size. Once a patient settles on a look that pleases them the
overall cup size increase becomes less relevant.With regards to your specific question, it is important to understand the concept of profiles. For a given volume a higher profile will be narrower with greater projection. Anecdotally speaking, most patients will do well with a moderate (+) profile device. I generally reserve high profile devices for my narrow framed individuals. The profile will not necessarily impact the "roundness" so much as projection or width.
As always, discuss your concerns with a board certified plastic
surgeon (ABPS).