I did not get to work with this koan as much as I would have liked, and basically felt that Nansen didn't need to be so harsh.
Maybe I'm just a softy for the cat, but isn't it kind of missing 'the point' of practice if we have to kill something innocent to prove it ? Even once he said he would cut the cat in half, did he really need to? Was it about sticking to his statement?
I could not work with the shoes-on-the-head part of the koan much at all, except that maybe he was using the only thing he had to try to symbolically protect himself from the run-away cutting of the monk. :)