Today I experimented the first time in the field with my self made nodal point adapter. The basis is a "MENGS" slide for tripods (manufacturer of cheap tripod stuff on amazon).
I adjusted the slide to remove the parallax error with two objects standing behind each other.
Today I took a trip outside, and checked if I could remain the same quality of images in the field like at home under "controlled" conditions. The result is this image:
(By the way, rain was comming up and it was just a quick test, so I did not bother for good exposure or even an HDR like shot...)
It was produced with the Canon 8-15mm f4.0 on a 5D mk ii using 12mm focal length. In hugin everything was quite straight forward. Using lens type "fisheye circular" and adjusted the crop, everything came out pretty good.
This setup gives me confidence, that it will work quite good - even in hurry and without using your brain too much.