Supposedly there's a crack for it, but I don't know anyone who has it.

I found a program called "The Mover" that partitions an 800k floppy into 5 140K partitions with a boot menu, but it failed to load Ultima 5. :/

Was worth a shot. Maybe someone will find the mod for it. In some of the old Computertist magazines there's an Q&A editorial about DinkeyDOS and its use with Ultima 5 and other games. Various mods were proposed, including one that seemed really cool, which was modifying it into thinking the required disks were actually directories. I have no idea what became of that.