I think the glider offerings by Lange Aviation were very original in thought and well executed, moved the lever forward, engine extracts and starts. The only problem is according to recent articles Lange has serious issues and customers have had to sue to get return of their money. Very sad. So the current offering of gliders have gas or jet engines. I did spend some time of the FES web site and it appears as if these units cannot be installed in Europe on certified gliders. Kind of limits the viability of yet another good idea.