there are plenty of ways to build a WTC. The best approach is to reserach, research and then research. There are plenty of websites on the internet and a lot of very experienced people.
you need to ask yourself what type of ballast system you want to use and the size of all the components that are involved. If you have an engineering bent then building your WTC is possible. I've built 2 that work really well.
This is the aussie subcommittee site and this page shows some of my stuff including the WTC.s I use the windscreen washer pump set up (sheerline) and i am quite pleased with it.
there are a couple of good books out there that i know of, norbert Bruggens model submairne technology is quite good although a bit mathematical it will give you all you need to think about but you can build without all the maths so don't stress.
The other traplet books are a bit of a waste of time. You have more pressing details to worry about than weathering a periscope!
I can certainly give more details of my set up if you wish, but there is a wealth of knowledge out there and learn as much as you can before deciding onyour configuration.
"Baldrick ,you would'nt recognise a subtle plan if it painted itself purple and danced on top a harpsichord singing "Subtle plans are here again!!" Blackadder.