Yes, that's right. When you said DD/DS floppies, I thought about the 3.5", not the 5.25".
Would an Apple SC20 drive, with a 5.25" Seagate drive work? I realize that these units are pre-SCSI, but I am thinking of other possibilities. I don't have access to a Profile drive (I have never even seen one personally), and I doubt that seller has one either. Again, if I do get the III, would a connection between a Plus, and a III be possible to transfer files, or am I going over my head?