Dave, that's an interesting movie.
http://en.wikipedia.org/wiki/Flettner_Fl_185
Re inverse taper that is just the price paid for increasing the cruise speed. Future technologies could include independant root and tip control, but best to get the concept flying reliably first. I think Nick's comments were more to with the fact that on any project 90% of the development happens as the prototype reveals the machines characteristics - you get what you can right before hand, but simulation doesn't always capture everything.