The total length of the short field stand is 55 cm, it also has a round disk at the end unlike the long stand that has disc with a piece cut away. On these early bikes the short field stand is clamped on the frame as in these photos. Not sure when they started brazing these brackets on the frame, it seems quite late during the war. As you can see even WM20 30775 still has it clamped on the frame, you can just see the clamp bolt. On the very early bikes it's also in a slightly different position, on the later bikes it's just about horizontal.