you don't need to worry that your selected female is or has the foundation , YOU need to have the foundation and that comes through experience. You need to know the blueprint of what you are trying to build - that is the only way to know what foundation you have .
Realistically you may trial and error more than one female , more than one combination of lines. You need to know what it is that you want to produce , recognize when you are NEAR and when you HAVE it . See - that is why one female appointed with "foundation" or best in titles, wins , conformation , may not produce what you want .
It is not even the best of the best of the best that will produce . No room to go anywhere .
When you have a litter you have to evaluate the success and quality of the litter over all , which you can not do until they are adults. Breeding is a lot of waiting in the bushes and observing , keeping mental notes. Old time dog-man saying is "now that WAS a good dog" , you only really appreciate the specialness towards the end when you review the progeny .
You move your agenda forward through the progeny that approximate and exceed your expectations.
You don't throw the baby out with the bath water .
You have to be very honest with yourself , critical , knowing how things have to be fine tuned , eliminated, brought back to preserve.
Then , the other half of the equation is following and understanding the males that you are using .
Since breeding involves repetitive use of family lines , as line or familial breeding then you need to thoroughly know the power of these genetics , good and bad , know when a combination is beneficial or trouble ahead.
Two good dogs , lines, could be great - but with other combinations, not thrown together .
Many breeders don't build on anything . Each breeding is a brand new experiment , single generation only.
What do Siberian breeders attempt to produce ? Is it a look , colour pattern, show structure ?
What is it that you want to do ?
Carmspack Working German Shepherd Dogs