This is a bit more math involved and about breeding Aussie's, but the same principles/rules apply to breeding Minis.
Playing COI: Using inbreeding Coefficients by C.A. Sharp
Breeding dogs is a numbers game. Even though math problems are the last thing on your mind, what you are doing when you breed is calculating the best odds for getting a desired result. But a little applied mathematics, in the form of a coefficient of inbreeding (COI) can be helpful and even enlightening. Now that technology allows even the mathematically challenged to put them to use, they are a tool that should be applied by every breeder. Research in the fields of genetics, immunology, and veterinary medicine, is turning up more and more information indicating that high levels of inbreeding can have deleterious effects on health. Inbreeding depression, a complex of behavioral and physical reproductive problems, have long been recognized. Inbreeding can increase the frequency of a disease in a population, sometimes quite rapidly. Inbreeding leads to increased incidence of immune-mediated disease and cancer. But, all pure breeds of domestic animals are inbred. (Keep in mind that to a scientist "inbreeding" means the breeding of related animals, which would include what we call "linebreeding"). But how much is too much? Without it, the breeds could never have been developed and would not breed true to type. However, almost all breeds of purebred dog already have well-established type. There is no mistaking a Chihuahua for a St. Bernard. Or even a Greyhound from a Whippet. Given this, breeders would be well advised to retain as much genetic diversity as possible within the existing breed population in order to avoid or reduce such unwanted health problems as those mentioned above. Along with screening and maintaining detailed health records, another tool available to you is the Coefficient of Inbreeding. Track COIs on your breeding stock. Calculate them on proposed matings, with an eye to keeping the numbers low if they already are or lowering them where possible.
Read the rest of the article here (highly recommend if you breed!)