My mate has a 5/8 3/8 out of reece's billy lines, 3 years old and that is doing more than asked of it. Puts 110 into everything it does out in field. Big build and head and is not stupid at all. Dont really know many dogs with well known lines but most of the bull crosses i know do exactly what they need to be properly. It goes to show its not about the dogs background, thats just something to have arguements with people about on threads like this.