Petter,
Try this URL, there is a construction article of the 'Amsterdam' which should answer some of your questions. As for towing, a lot of the people who do that modify the 'H' bar arrangement to extend to the bottom of the hull where it is braced and mounted. I'm sure there are other ways of doing it though. Good luck...
<http://www.marinerc.com/index.html>

Look under "Scale".

- LtDoc