Would I get more upper pole fullness if my implants were placed over the muscle?

I understand your concern. It might seem that placing the implant on top of the muscle would give a more round appearance. In reality, when implants are on top of the muscle, there is very little support to keep the implant high on the chest, and they invariable descend down the chest wall with in a few months. Remember, the skin is designed to stretch. In your case, I would change your implants to an ultra high-profile implant, perform lateral and inferior capsulorrhaphy (internal bra), mirror image capsulotomy, revise the mastopexy, and remove inferior pole breast tissue. This combination of surgeries is what I have termed "Reductive Augmentation" and I have developed this exact surgery over the last 14 years. I use it when a patient wants an much higher, rounder breast with upper pole fullness aka the "fake" look. Best of luck to you.

Placing the implants from behind the muscle to in-front of the muscle will not give you that 'augmented' look and will only cause more problems.  I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with.   Finally, make sure your surgeon is a Double-Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS), a member of the American Society of Plastic Surgery (ASPS) and the American Society of Aesthetic Plastic Surgery (ASAPS).Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach Trained, Double-Board Certified Plastic Surgeon

Thank you for the question and pictures.   Generally speaking, there are many long-term advantages of maintaining breast implants in the sub muscular position;  I would not recommend conversion to the sub glandular position. Some general thoughts regarding achieving the "fake look" may be helpful to you:
Many patients who are starting out with a significant amount of breast tissue and/or some “sagging”, will benefit from removal of some breast skin/tissue prior to undergoing breast augmentation surgery. Otherwise, they will likely not be pleased with the outcome of the procedure performed.
One analogy I used to describe the issues at hand is called the sheet versus comforter analogy. Young ladies who present with very little breast and/or adipose tissue “coverage” (analogous to "sheets") are more likely to achieve the “full, round” look with breast augmentation surgery since the breast implants will show themselves through the relative thin coverage present.
On the other hand, patients who present with more breast and/or adipose tissue coverage (“comforters”), are less likely to achieve the full round look after breast augmentation surgery, because the “roundness” of the breast implants does not show themselves through the relatively thick overlying coverage.
For these patients, who present with a significant amount of soft tissue coverage, traditional breast augmentation/lifting surgery may leave the patient dissatisfied, given that the “full, round” look is not achieved. One option for these patients is to remove breast tissue as well as breast skin during a breast reduction/lifting operation. By doing so, the plastic surgeon is essentially converting the patient from a “comforter” to a “sheet” situation. In my practice, I use a second stage breast augmentation procedure to achieve the “full, round” look that the patient is hoping for. During this stage, selection of breast implant type, profile, size etc. becomes important.  For patients seeking the "fake look", the use of over filled saline or ultra high profile silicone gel breast implants may be very helpful.  
I hope this, and the attached link, helps.