[5][6][7] When its performance proved inadequate for its intended role, even after numerous modifications, the German Inspectorate of Flying Troops (the Idflieg) eventually accepted it into service as a trainer.

[1][7] The design bore such a strong resemblance to the contemporary Sikorsky Ilya Muromets bombers produced in Russia that Jane's Encyclopedia of Aviation describes it as "virtually a copy" of that aircraft,[6] and in their book on German multi-engine types of World War I, Haddow and Grosz comment that designer Villehad Forssman "was content to copy the Sikorsky configuration almost line-for-line".

Wolff deleted the tacked-on pulpit from the nose and redesigned the forward fuselage to taper to a sharp point, surmounted by a teardrop-shaped cupola for the pilot.

[13] The outer engines remained unchanged, but were moved from their original position to mountings on faired struts midway in the interplane gap, to improve propeller efficiency.

[15] Reichel now offered Bruno and Franz Steffen ten percent of the sale price if they could perform an acceptance flight to meet the Idflieg's requirements.

[16] Franz's calculations based on the construction drawings showed the aircraft safe to fly, although the fuselage to be structurally weak immediately aft of the wings.

[16] After a successful 300-metre (984 ft) hop,[17] Bruno Steffen planned to fly the Forssman on its acceptance flight with four passengers aboard, as he had for his own R.I design.

[3][4] Further development of the design was halted, although the aircraft's ballast was moved to counter tail heaviness that Steffen encountered on the acceptance flight.