It's not rocket science...
Experiment until you find what you want, then line breed the
out of that, then cull ruthlessly until you've fixed type, then cull/refine until you've removed the major faults. By then you'll be 90 years old and can only hope that the next generation won't squander or abandon what you've spent your whole life building.
Hybrid vigor and in-breeding depression are very real, but they are also very over-blown. I don't understand why horsemen and houndsmen keep having the line-breeding/out-crossing debate. Line breeding is the only way to create reliable/predictable type, period. Intra-breed-out-crossing proponents like Pat Burns conveniently forget that they can get a lot of jam-up dogs from out-crossing now only because of all the hundreds of years of selective line breeding that went into their hounds/terriers/bird-dogs before they were even born that created large pools of prepotent stock among various breeds/types from which they can now "out-cross" <sigh>. It's like a trust-fund baby that thinks you don't have to work hard to be wealthy... he forgets that his granddaddy had to work hard to make all that money.
