Thinking about getting 500 cc hp silicone implants, under the muscle and not sure if it's going to be too big? (photos)

Thank you for the question and pictures. Base on your photographs, you are starting at a great place and should have a very nice outcome with breast augmentation surgery. I think your goal pictures are realistic and achievable. I share your concerns that 500cc may be too large for your frame however.  Despite good intentions, online consultants will not be able to provide you with  meaningful specific advice.  Ultimately, in person consultation with well experienced board-certified plastic surgeons will be necessary. Careful measurements, dimensional planning, and careful communication will be key.
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're 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 which operation and/or 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. I have found that the use of words such as “natural” or "C or D cup" etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup  size may also be inaccurate.  The use of computer imaging may be very helpful during this communication phase.
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.
I hope this, and the attached link, helps.

Of course you need an in person consultation with a board certified plastic surgeon to help you make your decision.That said based on the last photograph  which use seem to like and feel looks natural and full my guess is that a moderate profile plus silicone gel implant in the 350-400 cc range was used on her.  500 cc high profile implants are very large, will not have the natural cleavage and lateral or side breast fullness that you see in that photograph but will project more from the breast and will look more "augmented".

Every body type is a bit different.I prefer to utilize computer imaging to illustrate changes that may occur with different implants.The chages are illustrated on the individuals body.