I’m having some problems with the rear part of the chassis frame where the towing hook is. I find at least two different versions, maybe even three.
Tamiya made a bit U-shaped rear while Italeri made a square shaped rear for the Opel Blitz. I find both versions in photos.
I am not that knowledgeable about these vehicles.
I have been involved in the construction industry most of my life and recognize the how’s and why’s of structural shapes.
It is my understanding that German vehicles of this era had a type of coupler for towing that was sprung - hence the large hole in rear crossmember. IIRC they also had a funnel type of guard around the coupler that allowed the tow vehicle to simply back into the towed vehicle to connect - others more knowledgeable than I will be able to elaborate on this .
My thoughts is that its simply standard modifications done over the production run, simplification of parts, you see it a lot in Geman equipment. So would assume the more complex shape is the earlier model to the late simplified chassis.
That’s a late type chassis what see here, and IIRC the “bellied” channel was used to allow for a stronger setup and towing hook as the original was a bit weak for the usually overloaded trailers.