I am using Igo Primo2 but I have found the specs in the RAC4300 using Microsoft Sync to open it and looking in the Device.ini file.
That file contains the sys texts for a couple of devices, namely things like the Route66 Chicago,mini,maxi and Longhorn but also had the sys text for the RAC4300.
The issue was the port (com) setting.
For future reference:
Igo Primo2: port 7 baud 57600
RAC4300 Wide port 1 baud 57600.
So thanks for your post of three and a half years ago FF

All sorted and firing on all cylinders