I was just cleaning up some really old equipment at my Mom's house last night and ran across my old Courier modem as well. I remember paying big bucks for that sucker because of its upgradeable firmware (DSP?). Before that I was using an HST which was only good to connect to other HSTs. Such a shame that I will most likely end up tossing this in the bin.
Back in the day I used the HST a PC to download DMS files and then I had the null model cable connected to the Amiga. There was a special utility that ran on the PC and Amiga which allowed for max transfers between the two machines. All I remember was that the Amiga side would blank the screen during the transfers and the DMS file would magically appear in RAM: - From there I would expand the DMS to a disk. I remember it working very well and was much faster than using sneaker-net.