To continue using my 15Hitec RX's, I managed to buy an unused Hitec Flash 8 and an as new Flash 7 which do not have the problems identified in the Aurora 9. Interestingly, Hitec no longer make transmitters.
The Flash 7 and 8 differ from the Aurora in not having a touch screen and use a rotary dial like Spectrum.
With the Flash 7, the Dual Rate programme includes a panel to allow you to select and allocate a switch to operate it.
Surprisingly the Flash 8 is different - no switch option in the D/R section.
The manual advises you to select a switch before entering the D/R section but I can't find anything in the manual explaining how you do that !!!!!!
Clearly I am missing something obvious

Cheers
Paul