the num pad keypresses required to do this conflict with EZCA e.g. 2 & 5.
You mean the EZCA keys are conflicting with the GSX keys. We don't use any special keys, we just use the standard Slew keys.
I have tried turning off EZCA but this was only partly successful. Have you any suggestion in that regard?
Properly configure EZCA to be sure is not taking away any keys. Be sure no other addon is taking the same keys.
Also check in the Controls page, if Slew keys are set to default. In order to set all Slew keys to default, before pressing the Default button, you MUST first select the Slew events from the drop-down menu in the simulator Control setting page, because the Default button will reset only the page is currently set on.