no idea in modelling is a waste of time ya learn something new or get info for your subject,IMHO mirrors as walls may not work well, the vehicle is the center of the dio (sounds like it to me)and stands alone on the base,the viewer can walk around or look over the scene to see all sides(except the bottom) so showing the far side is unneccasary,however there is a dio out there of an aircraft factory where the side walls wre mirrors and it gave the viewer a sense of length(1 acft looked like 3),good luck on your second dio maybe we'll see it on the forums.always ask always learn,above all always have fun. happy modelling