Hay Michael,
This is link to this project. As I noticed latter there was little geometry imperfection, very little, you can see it by big magnification. I don know how it appears because this model was made not by me.
Any way even with this geometry imperfection it allows me to make solid. So I think this project allow you to taste your new tool in critical situation)
https://docs.google.com/file/d/0B1uI4ljG15POZmdVTENFZmx4WkE/edit?usp=sharing

Also I give you another model that I worked on. Here was a lot of blends with problematic connections. I gave here original model and model with delited blends. Also You can discover and delete some more blends for your work.
https://docs.google.com/file/d/0B1uI4ljG15POSEFKOTRkSTN5Q0k/edit?usp=sharing


Pillou, yes I think I was inspired from this trick in this tutorial)
I mostly work as 3D Artist, so for me all that looks like sphere is sphere :)))
If you are cad designer where 100% precision needed I don't know if it real sphere))) You can test it in rhino analysis tool, may be it will help)