Update;
I have been futzing around with AmigaExplorer from Cloanto, trying to get that to work through serial port and a null modem.
Unfortunately THIS laptop only has USB connectors and a built in modem that "gets in the way" by having COM 3 assigned to it.
I got a generic USB to serial adapter and got all cabled up with the null modem, but that wasn't working at all until I un-installed the built in modem and (after a few re-boots) managed to get the USB to serial adapter on COM3.
The AExplorer setup now "works" in that it recognizes the (physical) Amiga and the physical Amiga does receive data on SER: - - but it is flakey as all heck, sometimes I get 1800 or so bytes on the initial setup transfer, other times it is less than 400.
I have tried all the old tricks of moving the serial cable away from 110 volt power cables and away from the sheet metal cabinet of the Amiga, draping the (very short) USB cable carefully straight out from the laptop, etc., so I don't think it is a cable noise problem. I have also tried transfer speeds down to 300 baud. The 10ft Serial cable is the one I used to hook to a modem for dial-up, so I am confident that it works.....
Wow, memories,,, the number of Fish disks that passed through that cable.
Anyway, right now I think I'm going to revert to dial up with the old Zoom 28.8 modem, FTP .adf files of the SAS/C kit to my web site (private area) and FTP them back down with the Laptop.
Once I get an adf file maker running on the Amiga, I am able to write 720K floppies with this laptop and I can read them with CrossDos on the physical Amiga, so getting stuff from Aminet isn't TOO bad.
I should add; KUDOS to Cloanto and their retro platforms help desk, their technician Mike has been leaning over backwards on this for me.