Axil, The only disagreement I have with your position is Rydberg vs Inverse Rydberg - I won't say Rydberg gas atoms aren't involved [in fact it may be a push pull relationship] but I think they only occur on the surfaces you describe OUTSIDE the Casimir cavity and you are denying yourself a whole lot of usable surface area in the metal foam you described. IMHO rydberg atoms are responsible for the claims of slightly delayed half lives in radioactive gases while the claims of much more pronounced accelerated half lives are associated with Inverse Rydberg gas atoms INSIDE the Casimir geometry. This in keeping with my posit that Casimir force results in SEGREGATION of vacuum wavelengths NOT the simple displacement held by mainstream Casimir theory, The wavelengths pile up "just" outside the boundary to push these "apparently" shorter wavelengths through the cavity. I am convinced the "displacement" is actually a relativistic symmetrical Lorentzian contraction and that both types of Rydberg would appear smaller from the perspective of our ambient energy density for the same reason both "remote" observers appear smaller and slower to each other in the Twin paradox regardless of who is accelerated. I believe vacuum energy density increases and time slows for rydberg [similar to gravity well] and density decreases and time accelerates for inverse Rydberg [similar to a gravity warp or hill]. The segregation I mentioned means the concentrated low energy density between the boundaries is exactly balanced by a high energy density in a very near field on the outside surface of the mirrors. Perhaps we need to consider some sort of linkage between these different type of Rydberg gas atoms without and within that might allow a controlled asymmetry - Heisenberg trap? The mirrors obviously exert a quantum force on both by modifying energy density and breaking the isotropy at other than the square law of a gravitational gradient. Could the tail be wagging the dog in so far as condensed hydrogen or super atoms in both regions could be interacting by modifying the Casimir effect - perhaps creating instabilities between super atoms that seek out the least resistive path to decay within their combined structures?
BTW if I am correct about the relativistic aspects of the metal foam you describe it could produce mirror boundaries separated by less than atomic widths from our perspective yet still contain numerous fractional hydrogen atoms between said boundaries due to a symmetrical lorentzian contraction where energy density has been modified by suppression instead of velocity - the end result is v^2/C^2 is still modified but it is now the y axis itself being modified so there is no Pythagorean penalty AND all spatial axis appear to shrink equally from the perspective of an observer in any other frame. Regards Fran In addition as time goes by through the continuing action of heat, I speculate that the double tiered nano/micro particles would tend to weld themselves together at their contact points to form a kind of micro dimensioned porous metal-foam further reducing the total available surface area.