As Lexe says above, use bands to map the thumb slew.
Example from working profile:
Ministick X Axis CHANGE from Fallback TO Bands
This defaults to 3 bands, 0-33%, 34-66%, and 67-100%
Pushing the ministick puts it in one of the end ranges, releasing puts it in centre band.
Map comma "," to mini x axis band 0-33
Leave 33-66% band null for centering
Map forwardslash "/" to mini x axis band 67-100
Do same for the Y ministick axis, which uses semi colon and period (";" and ".") for 0-33 and 67-100 bands respectively.