I'm not sure whippets of any breeding could hold the bulk to which a cattle dog would add,border crosses nearly always to heavey to be useful and they aren't as heavey as an aussie type,would any one put an alsation to a whippet?,just can't see it working,
Where as a nice size greyhound would generate better length and hight,adding more weight to something already highly strung like a whippet could create yappers when on pressure runs.