In games with only two gears (e.g. 'Le Mans 24'), InputGearShift1 maps to 'Up' and InputGearShift2 to 'Down'.
Unlike what the readme says, Shift 1 and Shift 2 do not double as Up and Down in games like Le Mans 24 in Supermodel r741 while using Xinput. At the same time, trying to replicate that effect by manually mapping buttons results in conflicting inputs in games with 4 speed shifters, since Shift 1/Shift Up and Shift 2/Shift Down are used simultaneously. The end result is that I have to use sequential gears for everything, or map the 4 speed positions and run AT in games with Up/Down.