By this time in 1944 Lippisch realised that the war was hopeless and was happy to oblige, arranging for them to build a full-scale aerodynamic test glider for the P.12/13a project.

At Prien, Wolfgang Heinemann and Hans Zacher from Darmstadt, with Klaus Metzner and Hermann Nenninger from Munich, continued the work.

After occupation by U.S. troops in May 1945, work continued at the DM-1 on behalf of the U.S. military government, with General Patton and Charles Lindbergh visiting Prien to see the project.

Completed in early November 1945, the DM-1 was shipped in a wooden box to Langley Field in Virginia where the flow behaviour of the DM-1 was examined in the NACA (National Advisory Committee for Aeronautics, forerunner of today's NASA) full-size wind tunnel.

The cause proved to be vortex lift generated by the models which, due to its much higher Reynolds number, the full-size aircraft did not produce.

[4] The large and even thicker vertical stabilizer was removed and replaced with one of much smaller size, along with a cockpit canopy from a Lockheed P-80 Shooting Star in a more conventional position.