"We know that by using outbreeding or outcrossing we cannot hope too much for the mating to produce offspring that will have dominance, or hope to fix specific characteristics in the line.
Only by reducing the genetic pool by duplicating superior ancestors can certain gene groupings be reinforced - hopefully at double strength for dominance.
Outstanding performers tracing from female lines not having produced good sires usually are not successful when they go to stud. There are always exceptions though.
Outbred performers represent a big risk as breeding stock; inbred or linebred performers with a superior ancestor duplicated represent a lesser risk and sires
from female lines that have previously produced good sires, hardly any risk.