Not much on the way of write-up, but just a quick suggestion since the Onstar systems for our cars are completely useless now, but here is what I did to make use of the cover, and provide some added safety in the meantime:
As you can see, this $20 harbor freight fire extinguisher fits great under the cover with slight modifications. All I did was trim to about 1/2" thickness around the trim on the hinge side and removed the "shelf" the onstar vcim bolts to to free up space for the fire extinguisher. I'm sure there's plenty of things you can hide under here, this was just what I wanted to cover up, so use your imagination and post your ideas here!