I like Al Lynn's alot and honest on Selection of Stock .
But it seems you Must keep the Entire litters of your first Crosses till their old enough to Cull to the desired trates to Inbreed on. I gess I'am guilty of Selling too many and not keeping enough to Start right . I usualy keep at least 2 from every litter but only based on what I'am seeing at 8 weeks old, When I should be waiting till 8 months or more.