We play a sport called flyball and it is necessary to the game to have a height dog.   These have been specifically bred  for sports to lower the height to allow the bigger dogs to jump lower and thusly be faster. We at OffOn do not have litters of mixed breeds but if you are interested can get you in touch with a very reputable breeder. 

Photos

"Matrix" FGDCH40 TFFC-1
She is a 3/4 Border

NETB I'm Outta Here TFP "Split"
She is a Borderstaffy