Personally and I do me just my personal opinion for what works for me we look for no inbreeding and limited to no line breeding in our lines. We have purchased line bred 4-5 before and the dog was not mentally sound. When you start breeding really close you are asking for problems! Maybe if you know the lines in and out you could get away with it once or twice. I do not know my lines well enough to be comfortable with anything but outcrossing. I cannot chance puppies coming out with unstable minds or unhealthy.