Here is what I'm planning to do now.
I found
this site with the tugboat model (Dundrym Bay) from similar
time to W.O. Decker. There are the plans of the model
too. The hull is different but similar. On page 43 and 44
of the rebuilding report I have few frames of the hull.
Then on page 49 I have the picture of full hull.
I will get the plans of "Dundrum Bay" and resize them in photoshop
to match what I have about W.O. Decker. This way I will have
the hull lines for my tug. It will be not exactly what it should be
but the model will be very small anyway so I think the result
will be OK.