For the model mount I used a tube with a 5/8" inner diameter. This allows the use of a 5/8" rod as the display stand. This was also a size we commonly used "back in the day" for model mounts as it allowed the use of standard stage grip equipment, which is based around a 5/8" diameter pin or pipe, to hold models for construction, painting and filming. I have a variety of grip equipment that proves helpful now as a model stand.