Jetro, there are quite alot of whippet dogs around the 22ish and bigger mark, even a few at 23, and bitches well over 21 to just under 22, all kc the last 30 ish years. The sire to my lad's kc whippet bitch is 22 3/4" tts. Her dam is exactly 20". His pup is almost 20" at the moment, and isn't 7 months til 2nd feb. I've owned some real crackers over the years that were all pretty big, with even the bitches being well over 21".
I don't know, as I've never been into racing, but I'm thinking that alot of the assumptions about whippets being small, fragile etc, came about from the yard/weight