I have done a few spheres of different sizes. I personally prefer longer throw lenses since the further the projector is, the less proportional the optical distortion. Nevertheless, I've done a few 0.8s as well.
If you want to blend an entire sphere you'll need to hit it from six projectors (4 sides, top, and bottom). I did part of this once (no top, just bottom).
The content creation was actually the hard part.
The content creation model was card board box style with a center square and four squares on each side of it which folded up. It was actually pretty tough and the innovation was applauded but I would have preferred setting for something much simpler.
Just try doing a linear wrap with four. If you absolutely must do full coverage, contact me and I'll give a little more detail.
I also strongly suggest trying a prototype first with a small sphere and some low power projectors somewhere off site.