WIP - Decided to augment my German bridging troops with a Pioneer Wagon based on something like this:
I used trailers without their "tops" and simply built a platform and added items. I used the bridging gear from the sdkfz 251's with that equipment (didn't want to use it all so skimped on using too many of the metal bridging elements...). I know it is not exactly the same trailer (dimensions or otherwise), but I am satisfied.
