@ the last unlogged in commenter
F cup is possible now. You are already at E cup, and can get to F cup from the Slime Queen's Core. Siphoning the core is just a bit odd and this page is not up to date. As far as I can tell, udner normal circumstances siphoning her core will raise the minimum breast size, i.e. the AA behaviour mentioned on this page, but if you are already at E-Cup it will actually raise you to F-Cup, but oddly enough does nothing if in between those sizes.