I've been using FlightGear flight simulator for a few months now, mostly in my Simpit but also to model a couple of aircraft. I'm very interested in the Spacek SD-1, and I've started making a FlightGear model of that aeroplane. You can download the current (very primitive) version by following This Link.
Screen Shots
Please note that only the Sd-1 is my own work, and it's just a grab-bag of parts of other people's FlightGear models.
I wasn't happy with the quality of the Pilot's Notes that were available for download (mostly unreadable low-resolution jpg scans), so I've taken the time to re-type a couple of them. These will be VERY helpful if you're trying to fly the aeroplanes they refer to in FlightGear (it's very big on "realism" over "ease of use"):