Why do...

[swampyankee]

The Do 335 had a cruciform arrangement, but the propeller behind meant things would be different anyway.

View attachment 464869

Frequently, on aircraft with pusher propellers, the lower fin is added to keep the propeller from contacting the ground.

Ed Lesher, with his Teal, used a vertical stabilizer below the fuselage, and Molt Taylor, with the Imp, Mini-imp, and Micro-imp used an inverted V-tail for the same reason.

 

[Zipper730]

Look at the picture. You thought wrong. Wing is down and ventral fins are still flat.

Okay, just out of curiosity who took that picture?