Your description of the GLINK-LT says jumpers J3 and J4 can be used to configure for 9600 baud but I can find nothing saying how they are to be configured.
I am using the GLINK-LT in the user port of my SX-64. It is connected via a standard telbbs cable (7 wires) to my PC running BBS Server. Communication between the GLINK-LT and BBS Server remains at 2400 baud whether the J3 and J4 jumpers are on or removed. If I set BBS Server for 9600 baud, the log reports "RS232 error. Framing error! (Check baud rate)".
If BBS Server is set for 2400 baud, all RS232 communication is good with the jumpers on or off.
All testing was done using the Image v2.0 BBS program.