XL breast implants over muscle? I recently got 825cc Motiva implants over muscle.

 It is not possible to provide you with precise advice without physical examination but it is generally possible to further increase breast size down the line.   Generally, patients with these sizes of breast implants tend to have breast implants replaced in the initially dissected pockets (conversion to the sub muscular pocket may be very challenging technically and potentially associated with increased risk of complications). Best wishes. 

It would be very difficult to give any assessment without an in-person examination or photos at the least. Implant size depends on various factors such as chest wall measurement, tissue elasticity, your desired results, and the technique and skill of your surgeon. All of which can be assessed during a thorough examination.The best course of action would be to schedule an appointment with a board certified plastic surgeon for an in-person examination and a detailed discussion of your surgical options.