potential cross question

Reuben would you mind tellin me why they would loose there speed and agility? Is it a weight issue ? Im not doubting that fact . Just curious to the reasoning. Hes pretty tall but a slim dog. And hes pretty much all leg. I will try to figure out how to post pictures from my cell phone and show yall the "potential cross". And mike thats a good looking dog. Hate that he got run over. I hate to lose a dog that I have high hopes for. I went 4 and a half hours south of where I live once and picked up a pup out of some proven dogs and she got killed before she ever had a chance . Thats the way it goes I reckon.