I tried in Aerosoft Twin Otter. R is selected for sim rate. Inc./Dec. sim rate were blank. Even with that I could change sim rate 2×, 4x. But if I bind 'ctrl num+' for increase and 'ctrl num-' for decrease, sim rate increase to 4x, 16x with each input for Twin Otter! I haven't tried that with A310. What should I do?
For reference only I can mention, in Fenix A320 there is an option in the FMS CDU maint. page to select Sim Rate 2x.