This was the reason I built the LowRider2 in the first place. Finally installed it today.
I planed and jointed 2 × 12" dimensional lumber (spruce I think) into a large blank, laser etched it on both sides and cut it out with the router. Final size is 5 feet wide. I finished it with many coats of spar urethane.
I used ESTLcam for everything,