The reason the images "differ in detail" is because there were two dummies built over a period of several weeks, and over the years they have "merged" into one boat with one story. Most of the contemporary accounts of the boats were borderline fiction. Some of the US soldiers involved in the incident referred to the boat as the "Black Terror," but Porter called it the USS Wooden Dummy. There is no good documentation anywhere for "Deluded People Cave In" being painted on the boat, other than the artist's conception drawing of the second dummy that appeared in "Harper's Weekly," along with a story that was small amounts of fact disguised nearly beyond recognition.

Your concept of the boats' appearances would be as good as anyone elses. You just need to roughen it up a bit. Scrap lumber sides, pork barrel chimneys, etc.

For a full account of Porter's infamous hoax, see pages 75-79 of "Earthen Walls, Iron Men: Fort DeRussy, Louisiana and the Defense of Red River," by Steven Mayeux (Univ. of Tennessee Press, 2007).