How much do I need to overfill a moderate round saline bag for "fake" looking breast implants? (Photos)

Hello, although overfilling implants does tend to give them a rounder look, it could also void the warranty or make them more prone to rupture.  Perhaps your PS can find a different option.

Thank you for the insightful question.  Much of the final outcome achieved with breast augmentation surgery depends on the patient's anatomic starting point.  In some ways, it may be more challenging to achieve an "fake look" when patients start out with a significant amount of native breast tissue.  Having said that, it is usually possible with careful dissection of breast implant pocket (I generally prefer the sub muscular pocket for most patients, including patients who are looking for a larger or more fake look)  and careful selection of appropriate breast implant type/size/profile to achieve the "fake" look.
 Generally speaking, patients attempting to achieve the "fake" look often benefit from the use of  higher profile silicone gel breast implants or overfilled saline filled breast implants.  
 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 “fake look” or "D or DD cup” 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.
I hope this (and the attached link, dedicated to "faker" breast augmentation surgery concerns) helps. Best wishes.