Nonsense values when using 'Set RC to Param'

I’m having trouble with the ‘Set RC to Param’ feature to control a binary parameter MAV_USEHILGPS. I do the following:

  • Set a radio channel to be ‘PARAM1 tuning channel’ in ‘Radio’ settings
  • Pick the parameter to RC control, and set up its RC to Param settings. I’ve tried a few but scale=1, center=0.5, Min=0, Max=1 seems most appropriate.
  • The parameter then responds to RC control, but not within the set range, for example varying between 0 and 1061624946.
  • When I go back to the RC to Param settings, they’ve changed themselves, for example to center=1065353216, min=2147483648, max=2147483647

Is there any way to make this work correctly?