I don't think they could get too much out of forcing a 2x2 board in their Armies on Parade. Most materials you could buy in home improvement store (plywood, glue, expanding foam, spray paint, etc) while you could buy some of the GW terrain to use. I think it may just be more bragging right as in "look at what my customers did' between store managers haha.
At least at the end of this you will have a cool display for your army. Also, did you put anything under the plasticard?
I didn't think of the bragging rights before, but I totally agree with your take. The local redshirt is happy where he is, but his boss, who's been sent here by GW and doesn't speak the local language(s)...there's definitely motivation for him to show off. Usually it's just meeting revenue targets, but an edge like pictures you can send to the corporate HQ to show off how you're driving customer satisfaction/enthusiasm, they do matter.
But I did think about your question even during the production process. No, I did not put anything under the plasticard to further support it. It did bend slightly. It's 1.2 mm thick, which is pretty thin, so I tested if the black undercoat would stick and not crack when I lifted it, like a waiter's tray, and wobbled it a bit. It passed that test. Then I applied GW Texture Paint, having settled on Stirland Mud. It seems to have strengthened the plasticard and it bends less now. The paint still hasn't cracked.
I've already smeared it completely with Stirland Mud, and will let it dry overnight before I drybrush it with Doombull Brown. I took pics along the way, will post tmw.