I am dubious as to whether it was fitted. I have recently built 2 kits of the aircraft in your pic, one in 72nd and one in 32, and will soon be doing another in 48th. The best pic i could find of that area on the aircraft was the one in white wash, and it doesn't look as though its fitted. If you look at this pic of a different subject, you can see it is not there.
This image is Rudel aircraft, the one the model you posted portrays.
Same aircraft with white wash.
I have not found any hard evidance. But i believe the extra weight of the armour plates was to much when added to the weight of the cannons.
On my 72nd kit the armour was molded on and i just left it. But on the 32nd and 48th they are fitted seperatly and i left them off the 32nd one and will do the same on the 48th.
I am a Norfolk man and i glory in being so
On the bench: Airfix 1/72nd Harrier GR.3/Fujimi 1/72nd Ju 87D-3