Perhaps you have seen the Discovery Channel series where they build full size replicas of D's designs. Here's one my son and I did for his class from scratch using some basic layout and drafting techniques. I scaled it approximately 1/35. The thing I think kept some of D's designs from being realized was the sheer size-to-weight ratio. They were simply to large and heavy to have been useful in anything other than hard, flat terrain. Try to employ this tank on sod or even slightly damp ground and it would have been hopelessly bogged down. Still, what a mind!