Hi and thanks everyone!!!
@DP: U16 is rated as an U13 type boat by Conway's, differing by being 8cm shorter (half a Pixel); the sole photograph I found of her looks pretty much like the line-drawing of U13 in Groener's book. If you have info on visible differences (maybe the photo IS U13, just wrongly labelled, happens all the time), please hit me with it!
The U142 and her sisters are stretched U139s; I've included them as a subtype of the U139 class.
@CraigH: There's always FD scale...