It probably needs StuffIt 5.5, which doesn't run on a 68000 like Mini vMac emulates.

I (with a MacBook Pro) have a modern version of StuffIt Expander and when I used Mini vMac I would decompress on my modern Mac, then use the terminal command "macbinary encode" to encode the file. Then used importFl to get it into Mini vMac.

Don't do this if you use a Windows or Linux PC thought; it may corrupt the file.

P.S. This is my first reply to someone else's thread!