Subfascial or under the muscle? (Photo)

I prefer under the muscle to give better upper breast fullness and hide the implant more with more tissue. However, your bases cannot be moved and you still will have some gap between your breasts.

Dear jenifferslifestyle,
I almost always place implants submuscular. It lowers the rate of capsular contracture significantly. In addition, it looks much more natural because the muscle provides covering over the implant so its not as round on the top. I've also noticed the implants drop less over time when they are protected under the muscle.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

Under the muscle has clear advantages including lower rates of capsular contracture, less implant visibility/palpability, and a more stable result over time in general. I would highly recommend placing the implant below the muscle for those reasons and that you are relatively thin.