I suppose you have figured out that you pry open a factory shell, dump the shot, replce the shot with a like weight of the size of your choosing, and recrimp the shell. Not bad for hunting volumes of shells.

We consider chamber pressure because it translates into barrel chamber area force and into chamber wall stress. The liners will reinforce the chamber (I'd guess they will take full chamber pressure without support, but would check with the maker). The pressure is bound to drop as the wad skirt enters the 16 bore part of the barrel. But, from what to what? Basically, I'd not risk a it unless I had good, proven data from the chamber adaptor maker.