Its a risky mating TBH, any faults in the linage will come to surface, you are going to Double on all problems good and bad. You really need to know a little about breeding and genetics before breeding this tight IMO.
But in saying that, ive seen outstanding results in this type of breeding, you will bring to surface unwanted characteristics from ressesive genes, its a great way to see what faults lie dormant in your stock as both sire and dam can carry dormant faults and this will bring it to the top.
Its one thing to do it but you would have to cull hard to start with.
Im putting