I got the MS FFB to work in MS Flight (only centering forces) by using the fsforce utility:
1) Launch MS Flight and start your situation/flight/mission
2) Now return to desktop, and start fsforce.exe (through menu, explorer, short cut, ...).
Fsforce will start up and show a window saying it waits for fsx - let it wait ... (do not close this window)
3) go back to MS Flight and the joystick now has centering forces (at least this is how it works for me)
The centering forces keep working for the whole MS Flight session, no matter how many more flights/misions/airplances are loaded. I tried the other way round (first start fsforce and then MS Flight), but this didn't work.
I have Win7 64bit.
I use MS Flight in full screen.