are under the muscle, I had the surgery
back in 2003. I do not have any troubles with breastfeeding. I have 525cc for each breast, which took me from a 32A to a 32D. My OB/GYN said that he knew cases were women went too large and ended up causing damage from stretching, but not in my case.
I had a friend in Atlanta that had her implants over the muscle, and the incision was around her nipple, and she still breastfed her baby without any problems.
I think you should be fine.