Hi GFR!
Very fine work! Great to see a profile showing the personal plane from Hans Dortenmann. Here you will find a great model showing that plane. It's built by Klaus Herold, a fellow of the www.rlm.at Website. http://www.rlm.at/cont/gal31_e.htm
Just one thing. The dirt of the exhaust gases looks a little bit strange.
Cheers, Simon