I've read that this is a really bad idea and results in a lot of complications.
On the other hand, it's probably way better than polypropylene "silly string" implants, which mostly create size by stimulating a pocket of body fluid build up (kind of a cyst).
afaik, you can get larger 'under the muscle' implants, as things stretch out.
also, most 'under the muscle' implants are actually "partially under, partially over". Basically a bilateral cut in the pectoral muscle, with the implant placed under the upper half, and exposed over the lower half. Apparently this can be adversely affected by things like exercise though.
I'm also wondering if you'd end up with a "2 ice cream scoops" aesthetic problem, if the implants were large?
So here's a question though, if you're getting implants above the muscle anyway, why not just make those twice as big, instead of doing an over/under sandwhich?
(sorry to be a downer hehe, I do love to theorycraft big boob science

Just not sure this is an ideal method. I'd be happy to be corrected if wrong

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