Frustrating couple of days, because the Speedbrake control wasn't work. Turns out there were multiple problems.

1. I was setting the value for speedbrake_ratio as an integer. Apparently this doesn't work, started working when I changed to float. The Raspberry Pi converts the boolean on/off from the switch to float properly. As long as the plugin copy of the a4SimConfig.json shows the simulation to need float.
2. I'm using Arduino Mega from the throttle quadrant. I connected the Speedbrake Open input to Arduino Digital channel 26, and for some reason the internal pullup resister either doesn't work, or is inadequate. Had to add another pullup resistor to +5.
3. The logic to respond to inNonZero was not properly working. As of this writing, this part seems to be configured correctly.