I split this out of the driving cab info thread. We have a whole forum now. A separate thread for every topic!
To answer your question, the centering spring should work the way you want. I used it that way on my old Momo wheel and have also used it on the G27.
I always activated it in the windows controller settings screen though. IIRC there is a checkbox for "enable centering"
I just left it on all the time by default.
Make sure if you're loading a different profile in profiler it isn't turning it off.