Omnibus core memory compatibility?

Hi folks, I have the following stuff: G104 X/Y drivers G227 Sense/Inhibit G619A 4K core stack The 4K stack is broken and lost forever. But I have a spare G646C "4K or 8" Stack sitting around. I *think* it has 8K. Does anyone know if I could use that stack with the rest of the package, using only 4K of the memory? Does anyone have schematics for the 8K core system? In my documentation I have only information about the 4K system. On Doug Jones' module list, there are mentioned 4K and 8K sense/inhibit boards. And there are mentioned X/Y driver boards, without 4K or 8K written on them. I would like to know how DEC expanded the core. Doubling X or Y lines would be the easiest. But why should that result in different sense/inhibit circuitry? The sense/inhibit connections look quite similar on both of my stacks... Or does everything change? Thanks for clarification :-) And if someone has a spare 4K stack, please contact me! The same for 8K sense/inhibit and X/Y drivers. Best wishes, Philipp :-)