I actually manufacture the following interfaces:
USB - which works with FMS and Realflight.
Joystick port - which works with FMS and Realflight.
Serial Pic - which works with FMS only.
Realflight parallel port - which works with Realflight only and allows all channels to be proportional.
You can contact me on adrianh@hillcraft.co.za or
I am in Cape Town, South africa.