Double bubble - silicone over the muscle. Should I go under the muscle? 1 1/2 year post BA. (photos)

I am sorry to hear about your concerns after breast augmentation surgery. 
As you state, you have "double bubble" and breast implant bottoming appearance after your revisionary surgery. A "double bubble" is a cosmetically undesirable circumstance for patients with breast implants, which occurs when the breast fails to take on the shape of the implant, resulting in the appearance of a visible line showing a separation between the bottom edge of the implant and the bottom edge of the natural breast.   Double bubble "deformities" may be more striking (visible) when breast implants have bottomed out.
 
There are several options when it comes to revisionary surgery to improve your outcome.  One option is to eliminate the pull of the pectorals major muscle either by completely releasing it or by suturing the muscle back down, thereby placing the breast implants  in the sub glandular position.  Patients who choose to have breast implants placed in the sub  glandular position should have enough breast tissue coverage to allow for this conversion. There are disadvantages of placing breast implants in the sub glandular position (such as increased risk of breast implant encapsulation) which should be considered as you make your decisions.
Another maneuver that may be helpful is raising the inframammary fold using capsulorraphy techniques. In my practice, this type of repair involves a two layer, permanent suture repair (reconstructing the inframammary fold areas). 
This procedure serves to reconstruct the lower poles of the breasts and prevent migration of the breast implants too far inferiorly. Associated issues with positioning of nipple/areola complexes should improve with this operation.
Sometimes, depending on factors such as quality of skin along the lower breast poles, additional support provided by acellular dermal matrix or biosynthetic mesh may be very helpful. I have also found the use of acellular dermal matrix very helpful in cases where the skin/tissues are very thin and in cases of recurrent breast implant displacement. The acellular dermal matrix helps improve contour, improves irregularities caused by the underlying breast implant and/or scar tissue, and provides additional support ("sling" effect) for the breast implants.
 
Best wishes.

Sorry fr the severe animation deformity with double bubble effect plus asymmetry. Only in person examination waked allow a determination of exact operations o offer in this scenario.