As with anything, your chance of success depends on
percentages in the litter(s) and
selection afterwards
There is no "one" answer; there is no "magic pill"
One person may succeed where you may fail ... or you may succeed where another one fails.
Those dogs are bred well enough to have a legit shot.
IFFFF the individuals you display are GOOD ENOUGH to warrant a line being bred off them, then give it a shot.
But if you're just trying to "build a line" off mediocre, nothing dogs, then why waste your time?
However, if the quality of the dogs is outstanding enough to warrant you devoting a lifetime of dedication to preserving it, then that alone demands you try to do so
Jack