I can't recall that particular launch appearing on Mayhem, but there are several build logs of plank on frame hulls. The Steam section seems a good place to start, as there is Jim Pope's Chimeara build and Jerry's steam launch Wear (just put steam launch Wear into the search box at the top of the page), as well as others. They should give you some steers until someone turns up who has built the Selway Fisher launch.
Have fun
Greg