Well, I don't know how Evergreen sheets of styrene are (only have that in strips and tubes) but Plastruct sheet is bendable up to a certain thickness. Most of your typical injected molded/slide molded styrene from plastic model kits is kinda fragile. This stuff is not.
Besides... there are members here that have build covers for their gearbox assemblies out of aluminum and they look so much better than this rather crude example, but it is very effective!
Jeff