According to Apple, 4.1 requires a Mac 512K. The 128k could go to System 3.2, Finder 5.3.
I have several versions of Mini vMac, compiled as different machines. When I try to boot 4.1 on a Mac 128Ke version of Mini vMac, it crashes.
Based on this, I would assume 4.1 needs more RAM, and bombs...