In most cases here cost is an important factor so if you can get that extra 100 watts by making it a foot bigger for $50 why spend $200 on special improvements to get the same 100 watts. Not sure why on turbines so many want perfection when imperfection made a little larger often gives the same results. I chased this rabbit of making it all perfect or as efficient as possible till I got into actually building turbines. It was a real eye opener both on what can be built and on how to build one. It usually boils down to what is easiest with the best results. With experience one can hopefully refine design so ease of build and efficiency go together.

You tend to learn more when building a turbine than months spent perfecting a design on paper. My advice (worth what it costs nothing) is pick a design, study build notes from someone who has built one, come up with ideas for improvement, build it then see if adding the improvements you want are worth doing.