^Ok, your point is well taken regarding falling off the shelf if the expanders got too big, but I'm fairly certain the shelf moves. As the implant expands, it pulls and stretches the surrounding tissue. We have very few, essentially Beshine, to guess how much this may take place, but if you look at her incisions, you see that over the past 17 years, they have moved a few inches outward. At first, it was the lateral aspect, indicative of her sideboobs expanding, but eventually, perhaps 5 years post-surgical, the incisions again looked equal distance from her chest wall, perhaps 1.5" away from the chest wall. Today, the scars are more in the neighborhood of 3" away from her chest wall, meaning that her boob growth is gradually pulling her surrounding skin.
Now, the lattice would be sutured over the interior surgical incision and secured to bone using braided suture and titanium screws. In the early days, if Beshine bent forward, you could see the braided suture raise the overlying skin. Today, only the right medial remains evident; it shouldn't, but I would bet some aspect of the bra slipped out of place very early. Because her implants are so enormous, rather than anchor to a axillary rib, the evidence strongly suggests superior shoulder; the medial to the first rib near the sternum. These are smart positionings as there is little chance of warping a rib beyond what the weight alone might do. Though you are not supposed to be able to see the braided suture lines, I have heard a few of our 3000+ girls mention that they can feel them move with their hand when their boobs sway.
So, at least with Beshine because of her enormous expansion, the evidence suggests and it is logical that the lattice is no longer against her chest wall, but probably at least 2-3" away and extending further the normal 4" lattice width, assuming she settled for a single width, which, TBH, I kinda doubt; thinking she went for extra lattice. I prefer to look at the lattice as essentially a boob hammock, and with Beshine, her hammock today may cradle her underboob from a couple inches from her chest wall, to at least 6" away from her chest wall, probably further. With so much of the implant supported, it isn't going anywhere
But she is an exception and I sincerely doubt others would experience any real movement beyond an inch, which still yields 5" of support, projectively speaking. Though I do not know, I suspect Allegra's projection isn't much past 8", which means her bra likely cradles half of that distance.