PBC,I was taught that if two dogs have the traits that you are looking for, you need to try them and see if the blood "nicks". If so, you can linebreed on the offspring by breeding the offspring to grandparents, uncles/aunts, cousins, etc. Breeding is trial and error in some cases and it takes years to perfect it. Try what you have and see what you get. Keep all of the pups and cull them. You might have something. There are dogs that have been bred in the past that were outstanding in their own right but didn't produce well. If you know the bloodlines that you are using, you are on the right track.