I think you are right about creating two lines, if you like the quality of the cocks from both mixes, one line will be heavy RB the other K.
If you add outside blood you would need to be very choosy. You want to add only blood that is compatible or complimentary to your goals, only blood that adds a missing element and then you will probably need to do some very careful back crossing.
If you add outside blood you would need to be very choosy. You want to add only blood that is compatible or complimentary to your goals, only blood that adds a missing element and then you will probably need to do some very careful back crossing.