Why's that, mate?
I've seen a few 1st cross whippet/collies that were very racy and quick/fast.
Not saying it can't happen, but I've personally not seen it.
I think plummer was the first person to decry 1st cross whippet/collies, as they 'didn't have the height or frame' to support that sort of breeding, pretty obvious years later, what he was up to, as he did all he could to support and further his mate hancock's puppy farming venture.