Lewis,
What you've posted below is a copyrighted image (as indicated by the water-mark).
After you edit it out, I'll remove my link to it as well.
As members in good standing of the forum, it's incumbent on us to respect the legal position of our host, Matrix Games.
ORIGINAL: Yoozername
ORIGINAL: Yoozername
Nice shot showing the overlapping armor even on a box mantlet...
Note that there appears to be overlap from the front piece of the mantlet and the rear large piece. There is also overlap between this structure and the vehicles superstructure.
Also note the U shaped brackets (there are four of them, two below not visable in pic) that attaches the mantlet to the StuK40 gun. I saw these in the model instructions posted above. These could possibly serve as a device that allows some amount of 'sprung' armored mass. It appears the mass of the mantlet, which includes that cylindrical barrel protector, front 50mm shield and back 50mm shield are hung by these brackets.
This pic shows the mounting points...
Edit: Removed the quote-link to a copyrighted photograph that was illegally posted to the forum. In the absence of effective moderation of the group, there was nothing else that I could do to set things right.
Government is the opiate of the masses.