.151 is out and includes this feature.
To repeat how to use it:
For example, to disable the toggle on the shifter in outrun, open /cfg/outrun.cfg and add toggle="no" to the port tag, like so:
<port tag=":SERVICE" type="P1_BUTTON1" mask="16" defvalue="0" toggle="no">
This will only make the game behave like it original did, so if you have a sequential shifter that returns to center, it's not going to help.
Most older games with a Hi/Lo shifter only had one switch. If the Hi switch wasn't being pressed, the game would default to Lo (or vice versa).
If you have a Hi/Lo or H shifter that stays in gear, then this will solve the toggle issue for you.