GOT IT!
While I was napping tonight I had a stroke of brilliance. It occurred to me that CSA are/were sharp fellas and would probably have produced a program for the MMR just as good as for the Derringer.
The Derringer's D3 program has a specific option to install system RAM: DRAM. So it stood to reason in my half-asleep mind that so would the MMR's configuration program.
Sure enough, I ran the "csa-mmr" program and received a listing of options:
SRAM - Install 512k Static Memory
SROM - Copy system ROM to 512k Static Memory
DRAM - Configure and install RAM to system
The boot disk only uses the SRAM and SROM options. Added DRAM, and voila! 4MB of FastRAM.
Thanks for the jolt, guys!