Could you use Shrinkwrap under Mini vMac to mount the 6.x image, and then use DiskDup+ or DiskCopy to create a 4.2 or raw image?
If you can find documentation for the DiskCopy 6.x format, maybe I can support it directly in the firmware.
If you can find documentation for the DiskCopy 6.x format, maybe I can support it directly in the firmware.