Turned out there was one more pointless roadblock in the way. Apparently the standard Ubuntu package for Netatalk, 2.2.1, has a known bug related to enumerating directory contents that only shows up when accessed via ddp. The Plus was logging onto a share fine, but actually trying to access it made the connection go "poof". (Sigh) So I built a custom package for 2.2.2 and *that* one works. Since then I've successfully managed to use Stuffit Expander in an emulator to unpack some .sits of Diskcopy 4.2 images and use the Plus to write them, with the result that the 512k can now do this:



Now I just need to get a bucketload more floppies. Whee!

(I am seeing a little bit of weirdness with the 512k, but that's another thread I suppose.)