We did have one, albeit a mini.
The State Inspectors hated us enough already for the low ground clearance.
Although we were legal as 4" is the minimum. The next truck will have more on aero thought & devices on the bottom.
Here is a build pic of it. Aluminum sheet over corrugated plastic, shown with the protective blue plastic still covering the white aluminum. Light & tough. The cut-outs were for radiator brackets that were flat on the bottom. So we basically had a belly-pan from the leading-edge to the front of the steering tires.
