The first (and only other) time I've ever been referred to Hugh Knight was when a colleague, a respected WMA instructor himself, showed me some print-outs of pages from Knight's website and asked, his voice dripping with contempt, whether Knight "looked like a martial artist".
Knight has a significant weight problem and I doubt that he is all that light on his pins. That said, from what little I've seen of him in action (on the video linked by Tyrsmann), his form, timing, co-ordination, balance etc. look fine to me.
I've known heavyweights who had extraordinary endurance and agility for their size. In fact, the single best MA instructor I know is morbidly obese. I was once told that yet another well-known instructor had said of this man (I'll call him Tom), "he's not a martial artist", simply because of his weight. I would beg to differ; Tom is astoundingly strong, but he's so damn good at what he does that he de-emphasizes his own strength. He's a profoundly expert teacher of combative movement who would be hell on wheels in a street fight, and he's "not a martial artist" because he's fat?
Gimme a break.