Jack, this is not meant to be rude in any way, but you do know how the reverse logic works in the Hotstart TBM, do you?
This is from the manual:
Please note that in the simulation, as in the real aircraft, you cannot move the throttle from the POWER range into the TAXI and REV ranges without lifting the flight idle lockout to get over the flight idle stop gate. To actuate this lockout, you will need to map a button or key to the sim/engines/thrust reverse toggle command (aka “Toggle thrust reversers”). Pressing this button or key will lift the lockout.
NOTE Activating the “reverse toggle” command does NOT engage reverse thrust. The default X-Plane behavior has been overridden by the TBM900 simulation to behave as in real life. Instead, activating this action simply lifts the lockout tab. You then need to move your throttle past the flight idle stop and into the TAXI or REV ranges. Once in the ranges, you can release the “reverse toggle” button/key. The lockout tab will not re-engage until you again transition the throttle into the POWER range.
This means all you need to do is to map your physical throttle axis as "throttle" in xplane, no curve whatsoever needed. It will control the whole range from alpha over beta to reverse, but to get into reverse you need to press a button which you have assigned to the "toggle reverse" command.