If this also doesn't work, I guess that Fiasco has a problem with 486s. Right now I cannot test this because I currently don't have a working 486, but I probably will get one the week after the next.
Many thanks for glinux.gz and the new grub-ext2fs-floppy.gz. Unfortunately I got the same result with both of those as I got before: I can boot with init=/bin/sh, but the machine reboots itself as soon as I try anything more difficult than cd, pwd or echo *.
Edmund