The tank itself is quite basic - the bigger the better is the golden rule! However there are limits on how small you can go before the errors become totally unhelpful. From the size of boat you want to test, you then work out what is the best / most cost effective sized model, and from that the clearances you need below and either side of the model, etc. There's quite a lot of literature about these aspects.
Then there's some practical considerations around wave damping how quickly you can repeat runs, etc. Agains lots of papers and makes a huge difference to the commercial viability of a facility.
But the real 'difference' between towing tanks is the sophistication of their carriages. Each tank has developed this and its data logging capability because this gives each tank it's 'unique selling point'. Even university tanks are in effect commercial enterprises and their ability to carry out any test project is a combination of lots of things including tank size, model making ability and above all, the capability of their carriage and their data interpretation skills. I don't think you'll find much detail or get much help about the finer details of some of this because test tanks are a cut throat business.
You'll certainly get no more from me!
