Brie Bridges, 700cc over the muscle with 600cc existing under the muscle:
https://youtu.be/TWV67B4hrU4
I would assume having an original set already healed in place means there isn't rubber on rubber so no risk of abrasion damage?
Great video, props to her for doing that, although I felt bad that she felt the need to be so apologetic for her weight and the need to put on makeup etc. I thought she looked great, period.
As for the silicone on silicone (not rubber on rubber per se), yeah I think that's a genuine concern. Not so sure that shell-on-shell abrasion is a massively huge concern, as silicone polymer tends to be a pretty rugged material. Perhaps the greater concern is if a shell slips out of position relative to the other shell...? How easy is it to correct this, and how likely is it to reoccur? There might also be an opportunity for the development of some material which when placed between 2 silicone polymer shells ends up creating a connection which becomes ridiculously resistant to typical shear forces. I'm thinking along the lines of a "dry adhesive" by virtue of relatively high contact (eg, gecko's toes) but without the addition of materials likely to be more fat- or water-soluble (and thus creating an undesirable dispersion of materials through the body). If this makes sense. Just spitballing here, I'm not a materials engineer.
Another risk possibility, effectively sandwiching tissue (muscle?) when placing one implant under and the other implant over; given sufficient pressure, I could see the "implant sandwich" possibly at least reducing the bloodflow to any tissues between the implants. Might lead to the sensation of cramping, but this is just wild speculation on my part. Probably depends to a large extent just how tight the tissues (eg, skin) which surround the stacked implants is, which would be more of a concern Day One and less so a couple months out.
As to her recommendation to calling around and asking whether the surgeon would consider going larger (to size <whatever>), that's exactly the approach we took back when we went down this path. Responses were almost exclusively a) a shocked "no he would never do that" or b) "that's a great question, would you like to schedule an appointment to have that discussion with the surgeon" (which IMO is just code for "let the surgeon talk her into a smaller, more ordinary size").
The rare stand-outs were "oh he definitely has experience with doing that and would do so again", which worked out to be an exceptionally short list. This entire experience was one of the driving forces behind why I created my website in the first place, ie, why can't the information just be "out there", rather than forcing every patient to go through the same sit-ups every time. While it's true that a patient armed with information can turn into an irritating know-it-all to a surgeon who has had to endure years of schooling and quite frankly sometimes grueling training, it's also baffling how the whole process creates deliberate pinch-points to discourage the dissemination of better knowledge and understanding.
Arguably the surgeons who do understand all this end up having to walk a fine line between helping to provide bespoke services while at the same time keeping their heads low so as to avoid attracting undue media attention. Which in turn forces future prospective patients to have to go through the same meandering research that their predecessors had to go through.
*sigh*