Since the interior of the Ausf C and D are very close. It is sometimes very confusing with historical photo regarding the seats - leather vs wood bench. We know they were leather to start with, but later switched to wood bench (probably to save resources) that was carried forward to the Ausf D production. Is this correct?
According to the Osprey book on the SdKfz 251 and "Schutzenpanzer", by Uwe Feist, the wooden slat seats were introduced with the Ausf D, as part of the process of simplifying production. They were far quicker and cheaper to manufacture than the combination of metal tubing, leather and horsehair required for the Ausf C's seats. I'd suggest it makes sense to provide the leather seats with the Ausf C, as it's another feature that distinguishes it from the Ausf D.
All parts in the Engineer variant (251/7) are of a new design - the bridges, wood planks and support. We've also included a sPzB 41 (with wheels for offloaded use) with the kit. Even though taking up a lot of sprue space, we have decided to include two upper hull pieces (Ausf C & D) with the Stummel kit; it will be a pity not to!
Excellent!
Incidentally, I also really like the "Flivo" version you've done (Flivos were Luftwaffe forward air-control personnel) - the retractable antenna looks especially cool. As I mentioned previously, the frame antenna was much more common on the Ausf C. This version would make a very nice subject for a diorama. Especially accompanied by some armoured cars (hint hint!).