I haven't heard of the longer fuselage but am curious if truly existed.
"Mechanic of World Aircraft vol 2" tells the basic difference between the model I and the model II ko(A) is the engine.
Its following model II otsu(B) is a reinforced version of the ko(A) equipped with the dive-brake to be used as a dive bomber.
Measurements show all same in the list.
Spec list based on the army manual which was edited by Takeo Doi- Ki48 designer of Kawasaki Aircraft in December 1943.
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Appearances of the model II otsu(B) as a dive bomber.
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