My friend Joe Malinchak is well know here in the US for his micro RC stuff and has been consulting with Gasparin for quite a while. He recently ordered a pair of G2.6 motors for a micro RC twin project. This Free Flight beauty was also in the box, wrapped as a Christmas present.
It is a commercial product, so I doubt plans for this exact engine are available. I have seen other plans online though. Check Google for "co2 engine plans"