Couldn't hold onto 75 more frames from the beginning of #10069: Geferulf's DOS System Shock in 02:30.029. Desyncs around frame 600 or so.
Saves 420 frames (5.992 seconds) over #10069: Geferulf's DOS System Shock in 02:30.029 by mashing RMB to defeat the final boss. More savings should be possible. Uses this disc, with BizHawk's Config>File Extensions>.iso set to DOS.