Switch to flip between 4mb and 1Mb

Does anyone know which MMU pin you cut to chop 3Mb away from a 4Mb STFM?  I read a couple of techie_alisons threads (very sadly shes no longer with us) and she mentioned pin 64 in one thread and pin 18, both refering to A9, I think one is on a SIMM and the other she might mean on the MMU (64?)?   Does anyone know if cutting A9 on the MMU will leave 1Mb?  And is it pin 64 on the STFM MMU?

Edit: Using Marpet - dont know if that helps?