I accidently inserted a 1.44MB Chikago disk and mounted it with "-t dosfs".

I presume you mean `-t msdosfs'.

   After some work (including rm -rf of a subtree on the disk that contains
   directories and files with long names, which failed, of course) I copied  a
   600 kB file to the disk. This never finished and I couldn't log in on other
   term's (I could type the login name and ENTER, but then nothing would happen).

I've not seen this.  Could you send me (FTP, mail, whatever) a
compressed image of a Chicago floppy, so I can reproduce it here?

	   Maybe the chikago file system changes should be integrated
	   into dosfs?

I haven't seen any information on the low-level changes.  Perhaps it
can be reversed-engineered easily.