Hello NZsnowman. That Type II was finished just a few weeks ago, and you will find it coincidentally in the upcoming issue of FineScale Modeler (May 2010 issue).
http://www.finescale.com/en/Videos/Issue%20Previews/2010/03/May%202010.aspxThe issue is not on the shelves yet, but should be arriving this week in the US and next week in other countries). The article covers the full building and painting of U-9. I have included templates in the article, but to answer your questions, the diameter on the base is 33mm, while the diameter across the top railings is 47mm. I based my measuremetns on conversion from photos and on the excellent reference of the Type II by Eberhard Rossler. The supports will be tricky but a lot of dry fitting and trimming should get you there. Hope this helps, and do not hesistate to email me if you need any other assitance.
Looks like you are doing U-18? That is a great subject and one that I thought initially I would do too. While I learned a lot about Type IIBs, I am still a newbie in this area but will do my best to answer. Happy U-Boat modelling! I will be at the upcoming BUFFCON Model Show on April 11 in Buffalo NY and entering it in the contest there with all the other great builds I expect to see from others! If you are in the Western NY area, this is a great show put on by the IPMS Niagara Frontier guys!
PS - I put in a plug for AMPS decals in the article which are great! I would have used the new detail set but it was unfortunately not ready when I started this model a while back ;( Cheers
Harvey Low (lowharvey@hotmail.com).
IPMS Toronto Canada