Natural looking if I go 450cc? For Petites 5'2", 110 lbs (Photo)

Thank you for the question and pictures. Online consultants will not be able to provide you with specific enough advice to be truly helpful. 

Generally speaking, the best online advice I can give to ladies who are considering revisionary breast augmentation surgery 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. I have found that the use of words such as “natural” or "up a cup size” 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.

3. Once you feel you have communicated your goals clearly, allow your chosen plastic surgeon to work with you in determining the best plan to achieve your goals.
I hope this, and the attached link (dedicated to revisionary breast augmentation surgery concerns), helps. Best wishes.

This is a difficult one to answer because as with everything beauty is in the eye of the beholder.  Your idea of fake might be different then someone elses.  I personally feel that 500cc will be too big on your petite frame but I would first want to see pictures of the look you wish to achieve before deciding if that's the right size for your desired look.  In addition this would require an in person exam to take a look at your current breast measurements to best evaluate.