Yeah, I had a smaller metal block for the sides before.
I rarely use both griddle and grill at the same time, so there is almost always an open burner and the space above and below. The larger block on the back is now bent back to the chassis, not a flap like I had.
The open bottom was a bigger issue. I spent 21 dollars on a 36x36 sheet of aluminum. It weighs very little, but with the bends is strong enough. The rivets came from a drawer in the garage, so basically free