Dennis, funny enough if you punch the numbers shrinkage is an issue despite the low shrinkage % stated.... that is if you are particular. Of course it is a function of dimensions.... In this case, more is not always good if you are trying to eliminate variables...
As you mentioned and commonly done, staged skim coating helps reduce the effects of shrinkage. Of course a person should be aware of how much time is required between the primary bedding and skim coating to ensure most shrinkage is over.
I'm afraid many users have had problems with incorrect mix times, incomplete mixes, air entrapment and lastly chemical attack. As we all know, pre- bore guides (and even during) many over zealous cleaning BR shooters found their bedding and glue jobs suddenly go sour or fail......
Cast pillars do work, but after weighing the pros/cons I stopped using them.