Styrene Chassis template.
The top section is the upper chassis, it connects behind the servo casing and links to the grey piece that holds the truck spacer. The bottom section is the lower chassis, it connects to the front bulkhead, right below the steering tie rod and links back to the lower collar that catches the truck spacer. It's designed this way so that it doesn't hinder articulation. The lower section is plenty narrow enough not to hinder the tires during turns and the upper section was chopped on until it functioned without hindering the tire steering. As soon as i get time, I'll dremel one out of some steel stock and slap it on.