So the old find yourself the best brood bitch you can possibly buy and breed her to the best performing male you can find that has some common dogs in the ancestry is not bad advice. Deductive reasoning can say that if the mother produces the head and brain in the foetus, that the paternal genes are forming the body and limbs. What I take from this is to try and get the gamest well bred gyp that you can find and breed it to the most ATHLETIC dog that you can find. The dam's mind will be there and the sires athleticism. Of course.. this is all theory and not set in stone. if I compare MAyday to Yellowbuck which were two of the BEST EVER, it would still be a super hard decision because Dolly was a rugged well built game to the bone gyp that was bred to Gr.Ch.Yellow, a performing high ability I'll do whatever it takes to figure you out dog. Yellowbuck, (One of the best of all times) was out of a cold Awwesome BAby (ROM) gyp bred to one of if not the best performing most athletic dogs of all times (Buck) . However the amazing thing is when Victor bred Blondie (littermate to Yellowbuck) to MAyday the results were ONCE IN A LIFETIME DOGS. The original Macho had it all, and if not for running into the dog that beat CML, Havannah Chico, and Strictly Business, would have made Gr.Ch. and not just 1XW. but he made ROM in just 4 breedings. His siter Macha produced Machobuck. I like the X-Factor theory, but like I said, it's much more complicated than that.