I think you're going to be very disappointed with your outcross to Black. You would get very nice type if your girl is truly show quality, but you're not going to get any color. When you mentioned the leakage, I'm clear on what type of leakage. If you're referring to silver leakage, you should be so lucky; if you're talking gold, that would depend on what and if either one or bother is carrying a gold gene. These look like nice Birchens, have you asked the breeder about Birchen pullets? I think any patterned variety is difficult to breed and come out with good quality and especially show quality birds. From what I can of these two, your cockerel with be very heavily marked and I would want to put him with an undermarked hen. I have bred solid black to my heavily marked Birchens, but they are solid black Birchens, meaning birds that came from Birchen matings, but display no pattern.