Founder of LMF
And just to give some idea of how bad or otherwise the problem is when photographing moving people, I spotted a Flickr gallery of a tennis tournament shot with the fp L:
There are some significantly distorted tennis rackets in some of the photos, but I didn't spot anything much in the players.
Here is a good example
SIGMA fp L
100-400mm F5-6.3 DG DN OS | Contemporary 020