After receiving some very helpful responses (Mark S., Uncle Michael, RJ) on the HS JDS plug-in subforum, I performed the following:
Disconnected my RC Systems TTS board from the SG Com 2 and followed the instructions in the JDS plug-in help file to install the JDS plug-in on the SG-IP Com 2 port.
It took a couple of restarts of HS and a restart of the SG-IP, but I have successfullly interfaced HS to the SG-IP through the SG Com 2 port.
I presently have WinEVM talking to the SG-IP WebXpander daughter card which communicates with the SG Com 1 port. So far, I have exercised both HS, WinEVM and the WebXpander interface without any incidents. Obviously I am not exercising all three at the same time and, who knows, there may be some long term issues that will only surface with continued use.
This success has given me the courage to install ML3C and ML3S to eventually replace the JDS HomeRunner and PocketWebX applications that I presently use to remotely communicate with the SG through the WebXpander.
Because I am using two different pcs to run WinEVM and HS, it looks like I will not have to use the software port splitter. I can access the SG-IP with either WinEVM on the serial port or through HS on the HS webpage interface.