Ironclads
I suspect that the problem is that in most cases nobody has any accurate ideas what the underwater parts of most of the Confederate ironclads looked like. Six (or so) were built on existing hulls and possibly could be reconstructed from them. The CSS Manassis was built on a tugboat, and maybe you could fake it with some generic tugboat hull. Like, let somebody prove you wrong! From what I read, things were pretty chaotic in the Confederacy, and things got lost. Don, Vancouver, USA