For those projects requiring more memory, I have created a daughter board. This board may have up to 4 memory chips, each providing 16MBits of memory (2M x 4).
The MESA boards have 24 signals on each of their connectors. Finding memory requiring 24 or less signals was the trick. The 2M x 4 configuration has 19 signals: 11 address, 4 data, RAS, CAS, WE, and OE. I select one of the 4 memory chips by providing separate CAS.