Even if you were going to cross breed to another line of quality dogs as you did Reuben wouldn't you purify the genes of the dog you choose the same way?Back to best daughter and granddaughter so on and so forth?
I would do it just as you are saying...but I wouldn't concentrate too much on the first cross...I would hope to purify the gene pool somewhat before I chose one as the one I want to reproduce...I think there are more than a few ways to breed better dogs...