Boys normally wear suspender pants crossed at the back. This was the normal alternative. It was also the practical approach to suspender pants. Otherwise the straps would not stay on a boy's shoulders and fall down. We note some boys, however, with the suspender pants crossed in the front, but this was much less common.
We notice a few boys wearing short pants where the suspenders are crossed in the front rather in the back. Almost all of the imaes we have seen are younger boys. We do not believe that this is a separate style, but rather a boy wearing a new page of suspender shirts such as the younger boy seen here (figure 1). The suspender straps were often too long on a new pair of suspender shorts. Mothers commonly bought a child's clothes in a large size so he could wear them longer. Crossing the suspender straps in front in fact allowed a boy to wear them at the proper waist level. The photograph here is unidentified. We believe the the boy is prbably German and photographed in the 1950s. It is a good example of a younger boy eraring suspender pants crossed in the front.
While the fronts of the various kinds of suspender pants are quite destinctive, the back are all identical--crossed suspenders. We have never seen any different style. We only have a limited number of images showing the backs of these pants, but all the ones we have seen show the suspender crossed in the backs. I believe the same is true for the same kind of suspender skirts.