Santa delivered this year and I'm now the proud owner of an Irix F/4 11mm Blackstone lens.
This lens has the widest FOV with the lowest distortion of any lens I'm aware of.
In case anyone is interested in this lens, I've posted a few insights on my blog:http://photography.grayheron.net/2017/12/understanding-irix-11mm-depth-of-field.html (http://photography.grayheron.net/2017/12/understanding-irix-11mm-depth-of-field.html)