Use an MCR player like or MSXPLAYer to test.
A North American (NTSC-U) save file will not work with a European (PAL) version of the game. gme to mcr converter work
The trickiest part was step 5: . Some MCRs are stored in “even/odd” byte pairs (two 8-bit ROMs acting as a 16-bit bus). GME is linear. The converter must de-interleave on write. I wrote a small state machine to track odd/even bytes across the Z80 region. Use an MCR player like or MSXPLAYer to test